Pointer detection apparatus and pointer detection method

ABSTRACT

A pointer detection apparatus and a pointer detection method of the cross point electrostatic coupling type are disclosed, by which a pointer on a conductor pattern can be detected at a higher speed. The pointer detection apparatus includes a conductor pattern, a spread code supplying circuit, a reception conductor selection circuit, an amplification circuit, an analog to digital conversion circuit, and a correlation value calculation circuit. The spread code supplying circuit supplies a plurality of spread codes at the same time. The correlation value calculation circuit determines correlation values between signals output from the analog to digital conversion circuit and the correlation calculation codes respectively corresponding to the spread codes. A pointer is detected based on the determined correlation values.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 fromJapanese Patent Application JP 2009-288273, filed in the Japanese PatentOffice on Dec. 18, 2009, the entire content of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a pointer detection apparatus and a pointerdetection method, and more particularly to a pointer detection apparatusand a pointer detection method wherein a plurality of pointers can bedetected at a high speed.

2. Description of the Related Art

Conventionally, for the detection of the position of a pointer used witha touch panel or a like apparatus, various sensor systems have beenproposed, such as a resistive film system, an electrostatic couplingsystem and an electrostatic capacitive system. In recent years, apointer detection apparatus of the electrostatic coupling system typehas been vigorously developed.

Electrostatic coupling systems are divided into two types including asurface capacitive type and a projected capacitive type. Anelectrostatic coupling system of the surface capacitive type is applied,for example, in an ATM (Automated Teller Machine), and that of theprojected capacitive type is applied, for example, in a mobile telephoneset. In both types, a variation of the electrostatic coupling statebetween a sensor electrode and a pointer such as a finger or anelectrostatic pen is detected in order to detect the position of thepointer.

A pointer detection apparatus of the projected capacitive electrostaticcoupling system includes an electrode formed in a predetermined pattern,for example, on a transparent substrate or a transparent film. Theapparatus detects a variation of the electrostatic coupling statebetween a pointer and the electrode when the pointer approaches theelectrode. For a pointer detection apparatus of this type, varioustechniques for optimizing the configuration have been proposed and aredisclosed, for example, in Japanese Patent Laid-Open Nos. 2003-22158,Hei 9-222947, and Hei 10-161795 (referred to as Patent Document 1, 2 and3, respectively, hereinafter). In particular, Patent Document 1discloses a code division multiplexing system which uses an orthogonalspread code. Patent Document 2 discloses a coordinate inputtingapparatus which uses a pseudo-random signal. Patent Document 3 disclosesa pen for use with an electrostatic capacitive coordinate apparatus.

A pointer detection apparatus of the type called cross pointelectrostatic coupling system has been developed from the projectedcapacitive type electrostatic coupling system. Here, operation of apointer detection apparatus of the cross point electrostatic couplingsystem is described briefly with reference to the accompanying drawings.FIG. 75A shows a general configuration of a sensor section andassociated elements of a pointer detection apparatus of the cross pointelectrostatic coupling system, and FIG. 75B illustrates an output signalwaveform of the pointer detection apparatus.

Referring to FIGS. 75A and 75B, a sensor section 900 includes atransmission conductor array 901 formed from a plurality of transmissionconductors 902, and a reception conductor array 903 formed from aplurality of reception conductors 904. An insulating film is formedbetween the transmission conductor array 901 and the reception conductorarray 903. The transmission conductors 902 have a predetermined shapeand extend in a predetermined direction, in FIG. 75A, in the directionindicated by an arrow mark X and are disposed in parallel to, and spacedapart by a predetermined distance from, each other. The receptionconductors 904 have a predetermined shape and extend in a directioncrossing the extension direction of the transmission conductors 902,that is, in the direction indicated by an arrow mark Y in FIG. 75A. Thereception conductors 904 are disposed in parallel to, and spaced apartby a predetermined distance from, each other.

In a pointer detection apparatus which uses the sensor section 900having the configuration described above, for example, a predeterminedsignal is supplied to a predetermined one of the transmission conductors902. A variation of current flowing to a cross point between thepredetermined transmission conductor 902, to which the predeterminedsignal is supplied, and a reception conductor 904 is detected at each ofall cross points of the predetermined transmission conductor 902 and thereception conductors 904. Here, at a position of the sensor section 900at which a pointer 910 such as a finger is placed, part of currentflowing to the transmission conductor 902 is shunted through the pointer910 and this changes the current flowing into the reception conductor904. Therefore, the position of the pointer 910 can be detected bydetecting a cross point between the transmission conductor 902, to whichthe signal is supplied, and the reception conductor 904, to which avarying amount of current flows into. Further, with a pointer detectionapparatus of the cross point electrostatic coupling system, simultaneousdetection of a plurality of pointers is possible because the currentvariation is detected for each of a plurality of cross points formed onthe sensor section 900.

The principle of position detection of the cross point electrostaticcoupling system is described more particularly. A case is consideredhere where a predetermined signal is supplied to the transmissionconductor Y₆ and a pointing position of the pointer 910 such as, forexample, a finger on the transmission conductor Y₆ is detected as seenin FIG. 75A. First, in the state where a signal is supplied to thetransmission conductor Y₆, the difference between currents flowing tothe reception conductors X₁ and X₂ is detected by means of adifferential amplifier 905. Then, after a predetermined interval oftime, the reception conductors to be connected to the differentialamplifier 905 are switched to the reception conductors X₂ and X₃, andthe difference between currents flowing through the reception conductorsX₂ and X₃ is detected. This operation is repeated up to the receptionconductor X_(M).

Then, a level variation of an output signal of the differentialamplifier 905 at the position of each of the cross points between thetransmission conductor Y₆ and the reception conductors is determined.FIG. 75B illustrates a characteristic of the level variation. Referringto FIG. 75B, the axis of abscissa of the illustrated characteristicrepresents detection signals output from the reception conductors X₁ toX_(M) when they are temporally successively selected and connected tothe differential amplifier 905. It is to be noted that a characteristicindicated by a broken line curve in FIG. 75B represents a levelvariation of the signal actually output from the differential amplifier905 and another characteristic indicated by a solid line curverepresents a variation of the integration value of the output signal ofthe differential amplifier 905.

Since the pointer or finger 910 is placed in proximity to the crosspoints between the transmission conductor Y₆ and the receptionconductors X₅ and X_(M-5), current flowing in the proximity of thesecross points varies. Therefore, as seen in FIG. 75B, the output signalof the differential amplifier 905 varies at positions corresponding topositions in proximity to the cross points between the transmissionconductor Y₆ and the reception conductors X₅ and X_(M-5), and theintegration value of the output signal varies. The position of thepointer 910 can be detected based on the variation of the integrationvalue. In the conventional pointer detection apparatus, such detectionas described above is carried out while successively switching thetransmission conductors to be used for the detection one by one.

SUMMARY OF THE INVENTION

A conventional pointer detection apparatus of the cross pointelectrostatic coupling system as described above carries out supply andreception processes of a signal for each of the transmission conductorsand the reception conductors, which define the cross points, to carryout a position detection process of a pointer. Therefore, it has aproblem in that, if the position detection process is carried out forall cross points, then a long period of time is required for theprocess. For example, if the sensor section includes 64 transmissionconductors and 128 reception conductors and the detection processingtime at each of the cross points is, for example, 256 μsec, then aperiod of time of approximately two seconds is required for detection atall cross points, that is, at totaling 8,192 cross points. Therefore,such conventional pointer detection apparatus is not suitable forpractical use.

It is an object of the present invention to provide a pointer detectionapparatus and a pointer detection method of the cross pointelectrostatic coupling system using which a pointer can be detected at ahigher speed.

According to an aspect of the present invention, there is provided apointer detection apparatus for detecting a pointer positioned on aconductor pattern including a plurality of first conductors disposed ina first direction and a plurality of second conductors disposed in asecond direction which crosses the first direction. The pointerdetection apparatus further includes a code supplying circuit having aplurality of code strings of different codes from each other forsupplying predetermined ones of the code strings to the first conductorsdisposed in the first direction and forming the conductor pattern. Thepointer detection apparatus also includes a correlation valuecalculation code supplying circuit for supplying correlation valuecalculation codes that respectively correspond to the code strings, anda correlation calculation circuit for carrying out correlationcalculation between signals produced in the second conductors disposedin the second direction and the correlation value calculation codes. Thepointer positioned on the conductor pattern is detected based on resultsof the correlation calculation carried out by the correlationcalculation circuit.

According to another aspect of the present invention, there is provideda pointer detection method for detecting a pointer positioned on aconductor pattern including a plurality of first conductors disposed ina first direction and a plurality of second conductors disposed in asecond direction which crosses the first direction. The method includesa code supplying step for supplying predetermined ones of a plurality ofcode strings of different codes from each other to the first conductorsdisposed in the first direction and forming the conductor pattern. Themethod further includes a correlation value calculation code supplyingstep for supplying correlation value calculation codes that respectivelycorrespond to the code strings. The method also includes a correlationcalculation processing step for carrying out correlation calculationbetween signals produced in the second conductors disposed in the seconddirection and the correlation value calculation codes. According to themethod, the pointer positioned on the conductor pattern is detectedbased on results of the correlation calculation carried out at thecorrelation calculation processing step.

In the pointer detection apparatus and the pointer detection methodaccording to various exemplary embodiments of the present invention, bysupplying a plurality of signals produced based on one or a plurality ofcode strings different from each other to a plurality of transmissionconductors at the same time, presence of a pointer on the conductorpattern as well as the pointing position of the pointer can be detected.In other words, a detection process for a pointer can be carried out atthe same time with regard to a plurality of cross points. Therefore,with the pointer detection apparatus and the pointer detection methodaccording to the present invention, presence of one or a plurality ofpointers and the pointing positions of the pointer(s) can be detected ata higher speed at the same time.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a pointer detection apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a schematic sectional view of a sensor section of the pointerdetection apparatus of FIG. 1;

FIG. 3 is a block diagram showing a general configuration of a spreadcode supplying circuit of the pointer detection apparatus of FIG. 1;

FIG. 4 is a diagrammatic view showing a general configuration of atransmission conductor selection circuit of the pointer detectionapparatus of FIG. 1;

FIG. 5 is a diagrammatic view illustrating spread code switchingoperation by a transmission section of the pointer detection apparatusof FIG. 1;

FIG. 6 is a diagrammatic view showing a general configuration of areception conductor selection circuit of the pointer detection apparatusof FIG. 1;

FIG. 7 is a diagrammatic view illustrating switching operation ofreception conductors by the reception section of the pointer detectionapparatus of FIG. 1;

FIG. 8 is a block diagram of a correlation value calculation circuit ofthe pointer detection apparatus of FIG. 1;

FIG. 9 is a similar view but showing another correlation valuecalculation circuit of the pointer detection apparatus of FIG. 1;

FIG. 10 is a block diagram showing a general configuration of an exampleof an internal configuration of a correlator of the correlation valuecalculation circuit of the pointer detection apparatus of FIG. 1;

FIGS. 11A to 11G are time charts illustrating operation of severalcomponents of the pointer detection apparatus of FIG. 1;

FIG. 12A is a schematic view illustrating an operation principle of thepointer detection apparatus of FIG. 1 where no pointer exists on thesensor section, and FIG. 12B is a similar view but illustrating anoperation principle of the pointer detection apparatus of FIG. 1 where apointer exists on the sensor section shown in FIG. 2;

FIG. 13A is a schematic view of the sensor section of the pointerdetection apparatus of FIG. 1 where no pointer exists on the sensorsection, and FIG. 13B is a graph illustrating a relationship between anoutput signal of the correlator of FIG. 10, obtained where no pointerexists on the sensor section, and a code number;

FIG. 14A is a schematic view of the sensor section of the pointerdetection apparatus of FIG. 1 where a pointer exists on the sensorsection, and FIG. 14B is a graph illustrating a relationship between anoutput signal of the correlator of FIG. 10, obtained where a pointerexists on the sensor section, and a code number;

FIG. 15 is a schematic view showing the sensor section of the pointerdetection apparatus of FIG. 1 where a pointer is placed alongpredetermined reception conductors;

FIG. 16A is a graph illustrating a relationship between an output signalof the reception conductors of the pointer detection apparatus of FIG. 1and a spread code where the spread code is supplied to transmissionconductors shown in FIG. 15 on which the pointer is placed, and FIG. 16Bis a graph illustrating a relationship between an output signal of thereception conductors and a spread code where the spread code is suppliedto transmission conductors shown in FIG. 15 on which no pointer isplaced;

FIG. 17A is a view illustrating an example of an Hadamard matrix of 16chips, FIG. 17B is a similar view but illustrating an example ofHadamard codes of 15 chips, and FIGS. 17C and 17D are waveform diagramsillustrating correlation values where the Hadamard codes illustrated inFIGS. 17A and 17B are used, respectively;

FIG. 18 is a flow chart illustrating a processing procedure for positiondetection by the pointer detection apparatus of FIG. 1;

FIG. 19A is a waveform diagram of a spread code before PSK modulation bya pointer detection apparatus according to a second embodiment of thepresent invention, and FIG. 19B is a waveform diagram of the spread codeof FIG. 19A after PSK modulation;

FIG. 20 is a schematic block diagram of the pointer detection apparatusaccording to the second embodiment;

FIG. 21 is a block diagram showing a spread code supplying circuit shownin FIG. 20;

FIG. 22 is a block diagram showing a correlation value calculationcircuit shown in FIG. 20;

FIG. 23A is a waveform diagram of a spread code before FSK modulation bya pointer detection apparatus according to a third embodiment of thepresent invention, and FIG. 23B is a waveform diagram of the spread codeof FIG. 23A after FSK modulation;

FIG. 24 is a block diagram showing a configuration of a spread codesupplying circuit according to the third embodiment of the presentinvention;

FIG. 25 is a block diagram showing a configuration of a correlationvalue calculation circuit according to the third embodiment;

FIG. 26 is a schematic view illustrating switching of transmissionconductors by a transmission conductor selection circuit according to amodification 1;

FIG. 27 is a diagrammatic block diagram showing a configuration of atransmission conductor selection circuit according to a modification 2;

FIG. 28 is a diagrammatic view illustrating switching of transmissionconductors by the transmission conductor selection circuit of FIG. 27;

FIG. 29 is a diagrammatic view illustrating switching of transmissionconductors by a transmission conductor selection circuit according to amodification 3;

FIG. 30 is a schematic block diagram of a reception conductor selectioncircuit according to a modification 4;

FIG. 31 is a diagrammatic view illustrating switching of receptionconductors by the reception conductor selection circuit shown in FIG.30;

FIG. 32 is a cross sectional view of a sensor section according to amodification 5;

FIGS. 33A and 33B are a cross sectional view and a perspective view,respectively, of a sensor section according to a modification 6;

FIG. 34A is a schematic view showing a general configuration of a sensorsection according to a modification 7, and FIG. 34B is an enlarged viewof a land conductor portion shown in FIG. 34A;

FIG. 35 is a schematic view showing a general configuration of a sensorsection according to a modification 8;

FIG. 36 is a schematic view showing a general configuration of a sensorsection according to a modification 9;

FIG. 37A is a schematic view showing a shape of transmission conductorsin the sensor section of FIG. 36, and FIG. 37B is an enlarged aschematic view showing arrangement of a transparent electrode film ofreception conductors in the sensor section;

FIG. 38 is a schematic view showing a general configuration of a sensorsection wherein reception conductors are formed concentrically accordingto a modification 10;

FIG. 39 is a block diagram showing a general configuration of areception section according to a modification 11;

FIG. 40 is a diagrammatic view of an amplification section wherein adifferential amplifier is used according to a modification 12;

FIG. 41 is a block diagram illustrating that the same spread code issupplied to two transmission conductors positioned adjacent to eachother according to a modification 13;

FIG. 42 is a diagrammatic view illustrating detection carried out usinga 2-input 1-output amplifier where the same spread code is applied totwo transmission conductors positioned adjacent to each other accordingto a modification 14;

FIG. 43 is a diagrammatic view illustrating detection carried out usingan amplifier where the same spread code is supplied to two transmissionconductors positioned adjacent to each other according to themodification 14;

FIGS. 44A and 44B are diagrammatic views illustrating switching of aspread code to be supplied to transmission conductors according to themodification 14;

FIGS. 45A to 45C are diagrammatic views illustrating different switchingof a spread code to be supplied to transmission conductors according tothe modification 14;

FIG. 46 is a diagrammatic view illustrating a relationship betweensupply of the same spread code to a plurality of transmission conductorsdisposed at intervals and reception of signals at a plurality ofreception conductors according to a modification 15;

FIG. 47A is a diagrammatic view showing a general configuration of amodification 16, and FIG. 47B is a waveform diagram illustrating awaveform of an output signal of a differential amplifier in themodification 16;

FIG. 48 is a circuit diagram showing a configuration of a transmissionconductor selection circuit in the modification 16;

FIG. 49 is a circuit diagram showing a configuration of a receptionsection in the modification 16;

FIG. 50A is a diagrammatic view illustrating supply of a spread code anda reversed code to four transmission conductors positioned adjacent toeach other according to a modification 17, and FIG. 50B is a waveformdiagram illustrating a waveform of an output signal of a differentialamplifier in the modification 17;

FIG. 51 is a diagrammatic view illustrating supply of a spread code anda reversed code to four transmission conductors positioned adjacent toeach other according to a modification 18;

FIG. 52 is a diagrammatic view illustrating a general configuration forsupply of a spread code and a reversed code to three transmissionconductors positioned adjacent to each other according to a modification19;

FIG. 53 is a schematic circuit diagram showing a general configurationof a transmission conductor selection circuit where a spread code and areversed code are supplied to three transmission conductors positionedadjacent to each other in the modification 19;

FIG. 54 is a block diagram showing a configuration of a receptionsection where a spread code and a reversed code are supplied to threetransmission conductors positioned adjacent to each other in themodification 19;

FIG. 55 is a diagrammatic view illustrating a general configuration forsupply of a spread code and a reversed code to three transmissionconductors positioned adjacent to each other according to a modification20;

FIGS. 56A, 56B and 57A, 57B are views illustrating a principle ofdiscrimination of a hovering state according to a modification 21;

FIG. 58 is a distribution diagram illustrating the principle ofdiscrimination of a hovering state in the modification 21;

FIGS. 59 and 60 are diagrammatic views illustrating different adjustmentmethods of the aperture ratio of a detection level distribution on adetection surface upon position detection according to a modification22;

FIG. 61 is a diagrammatic view illustrating an adjustment method of theaperture ratio of a detection level distribution on a detection surfaceupon position detection according to a modification 24;

FIG. 62 is a diagrammatic view illustrating an adjustment method of theaperture ratio of a detection level distribution on a detection surfaceupon position detection according to a modification 25;

FIG. 63 is a block diagram showing a general configuration of areception section according to a modification 26;

FIG. 64 is a block diagram showing a configuration of an absolute valuedetection circuit according to the modification 26;

FIG. 65A is a schematic view illustrating a manner wherein a spread codeis supplied to an arbitrary transmission conductor according to amodification 27, and FIG. 65B is a graph illustrating signals fromreception conductors where the spread code supplying manner of FIG. 65Ais used;

FIG. 66A is a schematic view illustrating a supplying method of a spreadcode according to the modification 27, and FIG. 66B is a graphillustrating signals from reception conductors where the supplyingmethod of FIG. 66A is used;

FIGS. 67 and 68 are diagrammatic views illustrating a principle ofdetermination of a pointing pressure of a pointer according to amodification 28;

FIG. 69 is a graph illustrating a procedure of determination of thevolume of a region defined by a level curved surface using trapezoidapproximation according to the modification 28;

FIG. 70 is a diagrammatic view illustrating a supply of spread codes todifferent transmission conductors, respectively, where a number ofspread codes equals to the number of transmission conductors accordingto a modification 29;

FIG. 71 is a block diagram showing a configuration of a correlationvalue calculation circuit according to the modification 29;

FIG. 72 is a block diagram showing a configuration of a pointerdetection apparatus according to a modification 30;

FIG. 73 is a diagrammatic view showing a general configuration of areception section according to the modification 30;

FIG. 74 is a diagrammatic view showing a general configuration of areception section according to a modification 31; and

FIG. 75A is a schematic view showing a general configuration of aconventional pointer detection apparatus, and FIG. 75B is a waveformdiagram of an output signal of the pointer detection apparatus of FIG.72A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, several embodiments of the present invention of apointer detection apparatus and a pointer detection method are describedwith reference to the accompanying drawings. The description is given inthe order given below. It is to be noted that, while the followingdescription is given using a pointer detection apparatus as an example,the present invention is not limited to the illustrated embodiments andcan be applied in various other apparatus as long as the apparatusdetect a pointer positioned in the proximity of, or in contact with, theapparatus.

1. First Embodiment: examples of a basic configuration;

2. Second Embodiment: examples of a configuration which uses aPSK-modulated spread code;

3. Third Embodiment: examples of a configuration which uses anFSK-modulated spread code;

4. Fourth Embodiment: different supplying methods of a spread code;

5. Fifth Embodiment: selection methods of a reception conductor;

6. Sixth Embodiment: different examples of a configuration of a sensorsection;

7. Seventh Embodiment: different examples of a configuration of anamplification circuit; and

8. Eighth Embodiment: detection of hovering.

1. First Embodiment Examples of a Basic Configuration

An example of a basic configuration of a pointer detection apparatus anda pointer detection method according to the present invention isdescribed with reference to FIGS. 1 to 18. It is to be noted that, as aposition detection method in the present invention, an electrostaticcoupling method is used for detecting the position of a pointer based onthe variation of an electrostatic coupling state between a transmissionconductor and a reception conductor of a sensor section. Further, in thepresent embodiment, an example of a configuration is described wherespread codes in the form of code strings are supplied at the same timeto all transmission conductors and signal detection is carried out atthe same time through all reception conductors.

[Configuration of the Pointer Detection Apparatus]

FIG. 1 shows a general configuration of the pointer detection apparatusaccording to the first embodiment of the present invention.

Referring to FIG. 1, the pointer detection apparatus 1 includes, asprincipal components thereof, a sensor section 100, a transmissionsection 200, a reception section 300, and a control circuit 40 forcontrolling operation of the transmission section 200 and the receptionsection 300. In the following, the components are describedindividually.

First, the configuration of the sensor section 100 is described withreference to FIGS. 1 and 2.

Referring first to FIG. 2, the sensor section 100 includes a firstsubstrate 15 in the form of a substantially flat plate, a transmissionconductor array 11 including a plurality of transmission conductors 12,a reception conductor array 13 including a plurality of receptionconductors 14, a spacer 16, and a second substrate 17 in the form of aflat plate. In the sensor section 100, the transmission conductors 12,spacer 16, reception conductors 14 and second substrate 17 are arrangedand formed in this order on the first substrate 15. Accordingly, thetransmission conductors 12 and the reception conductors 14 are disposedin an opposing relationship to each other with the spacer 16 interposedtherebetween.

A pointer such as a finger or an electrostatic pen is used on the secondsubstrate 17 side, that is, on the side opposite to the face of thesecond substrate 17 opposing the first substrate 15. Accordingly, thereception conductors 14 are disposed nearer to the detection face of thepointer detection apparatus 1 than the transmission conductors 12. Inone example, a known glass substrate having transparency is used to formthe first substrate 15 and the second substrate 17, though a substratein the form of a sheet or film made of a synthetic resin or the like mayalso be used in place of the glass substrate.

Each of the transmission conductors 12 and the reception conductors 14is formed from a transparent electrode film, for example, of an ITO(Indium Tin Oxide) film, a copper foil or the like. The electrodepatterns of the transmission conductors 12 can be formed, for example,in the following manner. First, an electrode film formed from any of thematerials described above is formed on the first substrate 15, forexample, by sputtering, vapor deposition, or (painting) application.Then, the formed electrode film is etched to form the predeterminedelectrode patterns. Electrode patterns of the reception conductors 14can be formed on the second substrate 17 in a similar manner. Where thetransmission conductors 12 and the reception conductors 14 are formedfrom a copper foil, it is also possible to use an ink jet printer tospray ink including copper particles to a glass plate or the like toform the predetermined electrode patterns. The transmission conductors12 and the reception conductors 14 can be formed, for example, as linearor line-shaped conductors. Further, the transmission conductors 12 maybe formed as a diamond shape, a linear pattern shape, or the like.

The spacer 16 can be formed from a synthetic resin material such as, forexample, PVB (Polyvinyl Butyral), EVA (Ethylene Vinyl AcetateCopolymer), an acrylic-based resin or the like. The spacer 16 mayotherwise be formed from a silicon resin having a high refractive index,that is, a high dielectric constant. Also, it is possible to form thespacer 16 from liquid such as oil having a high refractive index, thatis, a high dielectric constant. Where a material of a high refractiveindex is used to form the spacer 16 in this manner, the parallax by thespacer 16 can be suppressed and an optical characteristic is improved.

Where the spacer 16 is formed from a synthetic resin, it can be formed,for example, in the following manner. First, a plastic resin sheet issandwiched between the transmission conductors 12 and the receptionconductors 14. Then, while evacuation between the conductors is carriedout, pressurization and heating are carried out to form the spacer 16.Or, for example, a synthetic resin in the form of liquid may be suppliedinto the space between the transmission conductors 12 and the receptionconductors 14, which is thereafter solidified to form the spacer 16.

Referring back to FIG. 1, the transmission conductor array 11 includes,for example, 64 transmission conductors 12 extending in a predetermineddirection, in FIG. 1, in the direction indicated by an arrow mark X. Thetransmission conductors 12 are disposed in parallel to each other andare spaced apart by a predetermined distance from each other. Thereception conductor array 13 includes, for example, 128 receptionconductors 14 extending in a direction perpendicular to the extensiondirection of the transmission conductors 12, that is, in the directionindicated by an arrow mark Y in FIG. 1. The reception conductors 14 aredisposed in parallel to each other and are spaced apart by apredetermined relationship from each other. In the illustrated example,the transmission conductors 12 and the reception conductors 14 are eachformed from a conductor of a linear or plate shape. Where thetransmission conductor array 11 and the reception conductor array 13 aredisposed in an opposing relationship to each other with the spacer 16interposed therebetween as in the present example, a capacitor of 0.5 pFis formed at each of the cross points between the transmission conductorarray 11 and the reception conductor array 13.

Although it is described in the following description that thetransmission conductors 12 and the reception conductors 14 each formedin a linear shape are disposed so as to extend perpendicularly to eachother, the shape of the transmission conductors 12 and the receptionconductors 14 may vary suitably in accordance with a specificapplication of the invention. Further, in the transmission conductorarray 11 and the reception conductor array 13, the transmissionconductors 12 and the reception conductors 14 may be configured so as tocross each other at an angle other than the right angle, for example, inan obliquely crossing relationship with each other. Differentembodiments are hereinafter described. Further, for an improved electriccharacteristic, the reception conductors 14 should be formed with awidth smaller than that of the transmission conductors 12. This willreduce the floating capacitance, to thereby suppress noise which may mixinto the reception conductors 14.

The disposition distance, that is, the pitch, of both of thetransmission conductors 12 and the reception conductors 14 is 3.2 mm inone example. It is to be noted that the number and the pitch of thetransmission conductors 12 and the reception conductors 14 are notlimited to those specified above, and they may be set suitably inaccordance with the size of the sensor section 100, required detectionaccuracy, and so forth.

In the following description, the transmission conductors 12 which formthe transmission conductor array 11 are represented by indexes n rangingfrom “1” to “64,” in the order beginning with the transmission conductor12 which is positioned nearest to the reception section 300. Atransmission conductor 12 corresponding to index “n” is referred to astransmission conductor Y_(n). Similarly, in regard to the receptionconductor array 13, the reception conductors 14 are represented byindexes m ranging from “1” to “128” in the order beginning with thereception conductors 14 which is positioned farthest from thetransmission section 200. A reception conductor 14 corresponding toindex “m” is referred to as reception conductor X_(m).

In the present first embodiment, each of the transmission conductorarray 11 and the reception conductor array 13 is divided into 16 groupsor blocks. A group of the transmission conductor array 11 is hereinafterreferred to as a transmission block, and a group of the receptionconductor array 13 is hereinafter referred to as a detection block.

Each transmission block includes four transmission conductors 12. Inparticular, each transmission block includes four transmissionconductors 12 which are positioned adjacent to each other and,therefore, have indexes “n” that are consecutive. More particularly, inthe present embodiment, the transmission conductor array 11 is dividedinto transmission blocks {Y₁˜Y₄}, {Y₅˜Y₈}, . . . , {Y₅₇˜Y₆₀} and{Y₆₁˜Y₆₄}.

Similarly, each detection block includes eight reception conductors 14.In particular, each detection block includes eight reception conductors14 which are positioned adjacent to each other and, therefore, haveindexes “m” that are consecutive. More particularly, in the presentembodiment, the reception conductor array 13 is divided into detectionblocks {X₁˜X₈}, {X₉˜X₁₆}, . . . , {X₁₁₃˜X₁₂₀} and {X₁₂₁˜X₁₂₈}. However,the present invention is not limited to the configuration justdescribed, and the number of conductors in one group, the number ofgroups, and the form or arrangement of groups such as the positionalrelationship of the conductors belonging to the same group may bevariably set in accordance with the size of the sensor section 100, therequired detection speed, and so forth. Details are hereinafterdescribed.

Next, the transmission section 200 is described. Referring to FIG. 1,the transmission section 200 includes a spread code supplying circuit21, a transmission conductor selection circuit 22, and a clockgeneration circuit 23. The transmission conductor selection circuit 22,spread code supplying circuit 21 and clock generation circuit 23 arearranged in this order from the sensor section 100 side. The spread codesupplying circuit 21 is connected to the control circuit 40 and theclock generation circuit 23 hereinafter described, and receives a clocksignal output from the clock generation circuit 23. The clock signaloutput from the clock generation circuit 23 is input also to the controlcircuit 40 hereinafter described.

Now, the spread code supplying circuit 21 is described with reference toFIG. 3. FIG. 3 shows an example of a general configuration of the spreadcode supplying circuit 21.

The spread code supplying circuit 21 in the first embodiment is providedin order to supply a code having a predetermined number of bits, such asa spread code, to the transmission conductors 12 so that the valueobtained from a correlation value calculation circuit 34 of thereception section 300 hereinafter described will be a predeterminedvalue depending upon whether or not a pointer exists. The spread codesupplying circuit 21 includes, for example, a number of spread codeproduction circuits 24 that equals the number of the transmission blocksof the transmission conductor array 11, that is, 16 spread codeproduction circuits 24. The spread code production circuits 24 eachproduce a spread code C_(k) (k: integer from 1 to 16) having a fixedcode length of 2n bits (n: integer) under the control of the controlcircuit 40 hereinafter described. In particular, the spread codes C_(k)are produced by the spread code production circuits 24, respectively, insynchronism with a clock signal output from the clock generation circuit23, for example. The n-th chip of each of the spread codes C_(k)produced in this manner is output at a timing of a rising edge of theclock signal. The spread code supplying circuit 21 may be configureddifferently, for example, such that it stores data produced based onspread codes in a ROM or the like and controls the read address of theROM to output a suitable signal to be supplied to each transmissionconductor. In the following description, 16 spread codes produced by the16 spread code production circuits 24 are respectively referred to asspread codes C₁, C₂, C₃, . . . , C₁₆. As the 16 spread codes C₁ to C₁₆,for example, Hadamard codes synchronized with each other can be used.The Hadamard codes are hereinafter described.

As hereinafter described, spread codes modulated by PSK modulation, FSKmodulation, or some other modulation may be used. Further, since, in aradio communication technique which adopts CDMA, usage of the word“chip” is common, in the following description, the communication speedis referred to as a chip rate (i.e., the number of pulses in a code thatare transmitted/received per second (chips per second).

Now, the transmission conductor selection circuit 22 is described withreference to FIG. 4. FIG. 4 shows an internal configuration of thetransmission conductor selection circuit 22.

The transmission conductor selection circuit 22 is provided in order toselectively supply spread codes C₁ to C₁₆ supplied from the spread codesupplying circuit 21 to the transmission conductors 12. The transmissionconductors 12, which form the transmission conductor array 11, aredivided into 16 transmission blocks 25 each of which including fourtransmission conductors 12. The transmission conductor selection circuit22 includes a number of switches 22 a equal to the number oftransmission blocks 25, that is, 16 switches 22 a. Each of the switches22 a has four output terminals 22 b which are respectively connected tocorresponding ones of the transmission conductors 12. Each of theswitches 22 a further has one input terminal 22 c which is connected toan output terminal of a corresponding one of the spread code productioncircuits 24 of the spread code supplying circuit 21 shown in FIG. 3.Each of the switches 22 a connects, at a predetermined interval of time,particularly at an interval of time corresponding to 16 periods of theclock output from the clock generation circuit 23 in one example, aselected one of the transmission conductors 12 to an output terminal ofa corresponding one of the spread code production circuits 24 whichoutputs a predetermined spread code C_(k). The switching operation ofthe switches 22 a is controlled by the control circuit 40.

An example of the switching operation of the transmission conductorselection circuit 22 is described with reference to FIG. 5. It isassumed here that one of the transmission conductors 12 which has thehighest index in each of the transmission blocks 25, that is, thetransmission conductor Y₄, Y₈, . . . , Y₆₀ and Y₆₄, is connected to anoutput terminal of a corresponding one of the spread code productioncircuits 24 through a switch 22 a as illustrated in FIG. 4.

The spread codes C₁ to C₁₆ output from the spread code productioncircuits 24, which form the spread code supplying circuit 21, aresupplied at the same time to 16 transmission conductors 12 selected bythe switches 22 a of the transmission blocks 25. In this state, positiondetection of a pointer is carried out for a predetermined period oftime, that is, for a period of time corresponding to 16 periods of theclock in one example. Then, after the predetermined period of timepasses, that is, after supply of the spread codes C₁ to C₁₆ to thetransmission conductors 12 selected by the switches 22 a is completed,the switches 22 a change-over (switch) the spread code productioncircuits 24 to be connected to adjacent ones of the transmissionconductors 12 positioned in the direction in which the index ndecreases, that is, to the transmission conductors Y₃, Y₇, . . . , Y₅₉and Y₆₃. Then, after the switching, the spread codes C₁ to C₁₆ outputfrom the spread code production circuits 24 of the spread code supplyingcircuit 21 are supplied at the same time to the 16 selected transmissionconductors 12 to carry out position detection. These operations arerepeated to carry out supplying of spread codes.

After those transmission conductors 12 which have the lowest indexes inthe respective transmission blocks 25, that is, the transmissionconductors Y₁, Y₅, . . . , Y₅₇ and Y₆₁, are selected by the switches 22a to carry out supply of the spread codes C₁ to C₁₆, those transmissionconductors 12 having the highest indexes in the respective transmissionblocks 25 are again selected by the switches 22 a, and the operationsdescribed above are repeated in each group. It is to be noted that theprocedure of the switching operation of the transmission conductors 12is not limited to the example described above with reference to FIG. 5.For example, while the switching operation of the transmissionconductors 12 in FIG. 5 is carried out after the spread codes C_(k) tobe supplied to the individual transmission conductors 12 are supplied,the switching of transmission conductors 12 may also be carried outevery time one chip in each spread code is supplied. Other modificationsare hereinafter described in detail.

As described above, the plural transmission conductors 12 are dividedinto a plurality of groups each including a predetermined number M (M isan integer equal to or greater than 2 (M≧2); in the example of FIG. 5,M=4) of conductors. Then, the spread codes C₁ to C₁₆ produced by thespread code supplying circuit 21 are supplied to predetermined ones ofthe transmission conductors 12 which form the groups, and thetransmission conductors 12 to which the spread codes are to be suppliedin the respective groups are successively switched. Since thetransmission section 200 is configured in such a manner as describedabove, spread codes for position detection can be supplied at the sametime to a plurality of transmission conductors 12. Since, in the exampledescribed, 16 different spread codes are supplied at the same time, thetime required for transmission of a signal for position detection can bereduced to 1/16 of what was required in the prior art.

Now, the reception section 300 is described. Referring back to FIG. 1,the reception section 300 includes a reception conductor selectioncircuit 31, an amplification circuit 32, an A/D (Analog to Digital)conversion circuit section 33, a correlation value calculation circuit34, and a position detection circuit 35. A correlation value obtained bythe correlation value calculation circuit 34 of the reception section300 corresponds to a detection state of a pointer, based on which theposition of the pointer is calculated by the position detection circuit35.

Now, the reception conductor selection circuit 31 is described withreference to FIG. 6.

The reception conductors 14 which form the reception conductor array 13are divided into 16 detection blocks 36, each of which including eightreception conductors 14. The reception conductor selection circuit 31includes a number of switches 31 a equal to the number of the detectionblocks 36, that is, 16 switches 31 a. The switches 31 a are provided ina one-to-one corresponding relationship with the detection blocks 36 toswitch among those reception conductors 14 to be selected in each block,in accordance with a control signal of the control circuit 40hereinafter described.

Each of the switches 31 a has eight terminals 31 b on the input sidethereof, which are connected to corresponding ones of the receptionconductors 14. Each of the switches 31 a further has a terminal 31 c onthe output side thereof, which is connected to an input terminal of acorresponding one of I/V conversion circuits 32 a hereinafter described.Further, each of the switches 31 a switches among the receptionconductors 14 to be connected to a corresponding one of the I/Vconversion circuit 32 a at a predetermined interval of time, that is, ina period equal to four times that of the switching timing of theswitches 22 a of the transmission conductor selection circuit 22 in theillustrated example. Output signals of the I/V conversion circuits 32 aare output to the A/D conversion circuit 33 through a changeover switch32 d after it is amplified to a predetermined signal level by anamplifier (32 b).

Now, the switching operation of the reception conductor selectioncircuit 31 is described with reference to FIG. 7. It is assumed herethat, in the detection blocks 36, those reception conductors 14 havingthe lowest indexes, that is, the reception conductors X₁, X₉, . . . ,and X₁₂₁, are connected to the amplification circuit 32 through theswitches 31 a as seen in FIG. 6.

First, in the state illustrated in FIG. 6, the reception conductorselection circuit 31 selects a plurality of reception conductors 14 atthe same time such that output signals S₁, S₂, . . . , S₁₆ of thedetection blocks 36 (current signals) are obtained for a predeterminedperiod of time.

Then, after the predetermined period of time elapses, the switches 31 aof the reception conductor selection circuit 31 change (switch) toadjacent ones of the reception conductors 14 which are positioned in thedirection in which the index m increases, that is, to the receptionconductors X₂, X₁₀, . . . , and X₁₂₂. Then, new output signals S₁, S₂, .. . , S₁₆ output from the reception conductors X₂, X₃, . . . , X₁₁₄ andX₁₂₂ connected to the switches 31 a after the switching are obtained.Thereafter, the switches 31 a of the reception conductor selectioncircuit 31 repeat the switching operation as described above.

Then, the switches 31 a are connected to the reception conductors 14having the highest indexes in the respective detection blocks 36, thatis, to the reception conductors X₈, X₁₆, . . . , X₁₂₀ and X₁₂₈ such thatnew output signals output from the selected reception conductors X₈,X₁₆, . . . , X₁₂₀ and X₁₂₈ are obtained. Thereafter, the switches 31 aare connected to the reception conductors 14 having the lowest indexesin the individual detection blocks 36 again such that new output signalsoutput from the reception conductors 14 having the lowest indexes in thedetection blocks 36 are obtained. The operations described above arerepeated in the respective detection blocks 36. It is to be noted thatthose reception conductors 14 which are not selected by the switches 31a are preferably connected to an arbitrary reference potential or theground potential. Where the reception conductors 14 which are notselected by the switches 31 a are connected to an arbitrary referencepotential or the ground potential in this manner, noise can bedischarged into the reception conductors 14 in a non-selected state.Consequently, the noise resisting property of the pointer detectionapparatus can be improved. Also this arrangement helps reduce thewraparound of a transmission signal. The procedure of the switchingoperation of the reception conductors 14 is not limited to the exampledescribed above with reference to FIG. 7. Various modifications arehereinafter described in detail.

As described above, in the reception conductor selection circuit, thereception conductors 14 are divided into a plurality of groups eachincluding a predetermined number of conductors, and at least oneconductor in each group is selected and the selected conductor issuccessively switched among the conductors which form each group.According to the configuration described above, multiple output signalsfor position detection can be obtained at the same time from thereception conductor array 13. In the present first embodiment, since thereception conductor array 13 is divided into 16 groups, the timerequired for reception of signals for position detection can be reducedto 1/16 of what was required in the prior art.

Now, the amplification circuit 32 is described with reference to FIG. 6.The amplification circuit 32 converts current signals output from thereception conductors 14 into voltage signals, and amplifies the voltagesignals. The amplification circuit 32 includes a number of I/Vconversion circuits 32 a equal to the number of detection groups in thereception conductor array 13, that is, 16 I/V conversion circuits 32 a,and a changeover switch 32 d. One I/V conversion circuit 32 a isconnected to each of the detection blocks 36.

Each of the I/V conversion circuits 32 a includes an amplifier 32 b inthe form of an operational amplifier having one input and one output,and a capacitor 32 c connected to the amplifier 32 b. The I/V conversioncircuits 32 a convert the output signals S₁, S₂, . . . , S₁₆ of thedetection blocks 36, which form the reception conductor selectioncircuit 31, into voltage signals and output the voltage signals. It isto be noted that, a resistance element, a transistor, or the like (notshown) may be connected in parallel to the capacitor 32 c in order toadjust the dc bias.

The changeover switch 32 d successively switches among the I/Vconversion circuits 32 a to be connected to the A/D conversion circuit33 hereinafter described, after every predetermined interval of time, tooutput voltage signals output from the I/V conversion circuits 32 atime-divisionally to the A/D conversion circuit 33. Where theconfiguration just described is adopted, the reception section 300 needsonly one system of the A/D conversion circuit 33 and the correlationvalue calculation circuit 34. Therefore, the circuit configuration ofthe reception section 300 can be simplified. While the changeover switch32 d described above is provided in the amplification circuit 32, it mayotherwise be provided between the reception conductor selection circuit31 and the amplification circuit 32. Where the changeover switch 32 d isprovided between the reception conductor selection circuit 31 and theamplification circuit 32, it is not necessary to provide a number of I/Vconversion circuits 32 a equal to the number of switches 31 a in thereception conductor selection circuit 31. Consequently, the circuitconfiguration of the reception section 300 can be simplified. It is tobe noted that, while in the first embodiment described the changeoverswitch 32 d is provided so that only one system of the A/D conversioncircuit 33 and the correlation value calculation circuit 34 is provided,the present invention is not limited to this configuration, and a numberof A/D conversion circuits 33 and a number of correlation valuecalculation circuits 34 equal to the number of the I/V conversioncircuits 32 a, that is, 16 A/D conversion circuits 33 and 16 correlationvalue calculation circuits 34, may be provided. Such a configuration asjust described eliminates the need to carry out the switching control bymeans of the changeover switch 32 d, and therefore is suitable to form apointer detection circuit for which a higher speed signal processing isrequired.

The A/D conversion circuit section 33 is connected to an output terminalof the amplification circuit 32, and converts an analog signal outputfrom the amplification circuit 32 into a digital signal and outputs thedigital signal. The output signals S₁, S₂, . . . , S₁₆ converted intovoltage signals by the I/V conversion circuits 32 a are converted intoand output as digital signals by and from the A/D conversion circuit 33.It is to be noted that a known A/D converter can be used for the A/Dconversion circuit section 33.

Now, a configuration of the correlation value calculation circuit 34 isdescribed in detail with reference to FIG. 8. The correlation valuecalculation circuit 34 calculates correlation values from the outputsignals S₁, S₂, . . . , S₁₆ successively output from the A/D conversioncircuit 33. The correlation value calculation circuit 34 is connected tothe A/D conversion circuit 33, control circuit 40, and positiondetection circuit 35, which is hereinafter described, as shown in FIG.1.

The correlation value calculation circuit 34 includes a signal delaycircuit 34 a, a number of correlators 34 b ₁, 34 b ₂, 34 b ₃, . . . , 34b ₁₆ equal to the number of the spread codes C_(k), that is, 16correlators 34 b ₁, 34 b ₂, 34 b ₂, . . . , 34 b ₁₆, correlation valuecalculation code production circuits 34 c ₁, 34 c ₂, 34 c ₃, . . . , 34c ₁₅, 34 c ₁₆ for supplying correlation value calculation codes to thecorrelators 34 b ₁ to 34 b ₁₆, respectively, and a correlation valuestorage circuit 34 d.

The signal delay circuit 34 a temporarily retains digital signalssuccessively output from the A/D conversion circuit 33 and supplies theretained data simultaneously to the correlators 34 b ₁ to 34 b ₁₆. Thesignal delay circuit 34 a includes a number of D-flip-flop circuitsequal to the code length of the spread codes C_(k), that is, 16D-flip-flop circuits 34 a ₁, 34 a ₂, 34 a ₃, . . . , 34 a ₁₅, 34 a ₁₆.The D-flip-flop circuits 34 a ₁₆, 34 a ₁₅, 34 a ₁₄, . . . , 34 a ₃, 34 a₂, 34 a ₁ are connected in series and in this order from the A/Dconversion circuit 33 side. An output terminal of each of theD-flip-flop circuits 34 a ₁ to 34 a ₁₆ is connected to a neighboringnext one of the D-flip-flop circuits 34 a ₁ to 34 a ₁₆ (for example, theoutput terminal of the D-flip-flop circuit 34 a ₁₆ is connected to theD-flip-flop circuit 34 a ₁₅) and also to the correlators 34 b ₁ to 34 b₁₆. As illustrated, output signals of the D-flip-flop circuits 34 a ₁ to34 a ₁₆ are input to all of the correlators 34 b ₁ to 34 b ₁₆. Outputsignals consisting of 16 chips from the 16 D-flip-flop circuits 34 a ₁to 34 a ₁₆ are hereinafter referred to as output signals PS₁, PS₂, PS₃,. . . , PS₁₅, PS₁₆, respectively.

The correlators 34 b ₁ to 34 b ₁₆ multiply the output signals PS₁, PS₂,. . . , PS₁₆ output from the D-flip-flop circuits 34 a ₁ to 34 a ₁₆ bycorrelation value calculation codes C₁′ to C₁₆′, respectively, which areinput from the correlation value calculation code production circuits 34c ₁ to 34 c ₁₆, to produce and output the correlation value of each ofthe spread codes C_(k). Since the correlators 34 b ₁ to 34 b ₁₆ carryout correlation calculation for the spread codes C₁ to C₁₆,respectively, total 16 correlators 34 b ₁ to 34 b ₁₆ are provided. Inparticular, the correlator 34 b ₁ multiplies the output signals PS₁,PS₂, . . . , PS₁₆ from the D-flip-flop circuits 34 a ₁ to 34 a ₁₆ by thecorrelation value calculation code C₁′ to calculate a correlation value,and the correlator 34 b ₂ calculates a correlation value between theoutput signals PS₁, PS₂, . . . , PS₁₆ and the correlation valuecalculation code C₂′. Similar calculation is carried out untilcorrelation values regarding all of the 16 spread codes C₁ to C₁₆ arecalculated. Then, the correlators 34 b ₁ to 34 b ₁₆ output thecalculated correlation values to the correlation value storage circuit34 d.

The correlation value calculation code production circuits 34 c ₁, 34 c₂, 34 c ₃, . . . , 34 c ₁₅, 34 c ₁₆ supply correlation value calculationcodes C_(k)′ to be used for correlation calculation by the correlators34 b ₁ to 34 b ₁₆, respectively. The correlation value calculation codeproduction circuits 34 c ₁ to 34 c ₁₆ are connected to correspondingones of the correlators 34 b ₁ to 34 b ₁₆. The correlation calculationcodes C₁′ to C₁₆′ to be supplied from the correlation value calculationcode production circuits 34 c ₁ to 34 c ₁₆ to the correspondingcorrelators 34 b ₁ to 34 b ₁₆ have a code length of 2n. For example,since the correlator 34 b ₁ carries out correlation calculation of thespread code C₁, the correlation value calculation code C₁′ of 16 chips(PN₁, PN₂, PN₂, . . . , PN₁₅, PN₁₆) is supplied to the correlator 34 b₁. A correlation value calculation code supplied from each of thecorrelation value calculation code production circuits 34 c ₁ to 34 c ₁₆to a corresponding one of the correlators 34 b ₁ to 34 b ₁₆ ishereinafter represented by C_(x)′ (PN₁′, PN₂′, PN₃′, . . . , PN₁₅′,PN₁₆′).

Then, as the correlators 34 b ₁ to 34 b ₁₆ carry out correlationcalculation between the reception signals PS₁, PS₂, . . . , PS₁₆ and thecorrelation value calculation codes C₁′ to C₁₆′, if no pointer exists onthe sensor section 100, then correlation values of a fixed value areuniversally obtained. On the other hand, if a pointer 19 (see FIG. 12B)exists on the sensor section 100, then a correlation value having avalue different from the fixed value is obtained.

The correlation value storage circuit 34 d is a storage section fortemporarily storing correlation values obtained by the correlationcalculation by the correlators 34 b ₁ to 34 b ₁₆. The correlation valuestorage circuit 34 d is formed from a number of registers (not shown)equal to the number of the correlators 34 b ₁ to 34 b ₁₆. Since each ofthe transmission blocks 25 of the transmission conductor selectioncircuit 22 is formed from four transmission conductors 12, which areswitched between by a switch 22 a as described hereinabove withreference to FIGS. 4 and 5, if detection of a pointer is carried outwith one reception conductor 14, then four correlation values areobtained. Therefore, each of registers from which the correlation valuestorage circuit 34 d is formed has four regions. Into the four regions,correlation values obtained by the correlation calculation are storedrespectively. Accordingly, the registers store data for the cross pointsbetween an arbitrary one of the transmission conductors 12 and all ofthe reception conductors 14 which form the reception conductor array 13,that is, 128 data. The correlation value storage circuit 34 d thus mapsthe input correlation values at the cross points over the entire surfaceof the sensor section 100 to thereby produce a spatial distribution ormapping data of the correlation values.

Now, operation of the correlation value calculation circuit 34 isdescribed. The output signals S₁, S₂, . . . , S₁₆ of the I/V conversioncircuits 32 a are successively converted into digital signals by the A/Dconversion circuit 33 and input to the correlation value calculationcircuit 34. The first one of the digital signals input from the A/Dconversion circuit 33 to the correlation value calculation circuit 34 isfirst stored into the D-flip-flop circuit 34 a ₁₆ of the signal delaycircuit 34 a. Then, the D-flip-flop circuit 34 a ₁₆ supplies the storeddata to the correlators 34 b ₁ to 34 b ₁₆. Then, a next digital signaloutput from the A/D conversion circuit 33 is supplied to the D-flip-flopcircuit 34 a ₁₆, and thereupon, the D-flip-flop circuit 34 a ₁₆ outputsthe data stored therein to the adjacent D-flip-flop circuit 34 a ₁₅, andstores the newly supplied digital signal and outputs the newly storeddata to the correlators 34 b ₁ to 34 b ₁₆. Thereafter, every time newdata is input, the D-flip-flop circuits 34 a ₁ to 34 a ₁₆ repeat theprocess of outputting data stored therein to the adjacent D-flip-flopcircuits and the correlators 34 b ₁ to 34 b ₁₆ and storing the newlysupplied digital signals.

The output signals PS₁ to PS₁₆ of the 16-chip length stored in theD-flip-flop circuits 34 a ₁ to 34 a ₁₆ are supplied to the 16correlators 34 b ₁ to 34 b ₁₆, respectively. The correlators 34 b ₁ to34 b ₁₆ carry out correlation calculation between the output signals PS₁to PS₁₆ supplied from the D-flip-flop circuits 34 a ₁ to 34 a ₁₆ and thecorrelation value calculation codes C₁′ to C₁₆′ supplied from thecorrelation value calculation code production circuits 34 c ₁ to 34 c ₁₆to respectively obtain correlation values.

Then, the correlators 34 b ₁ to 34 b ₁₆ output only the correlationvalues obtained as a result of the 16th calculation to the correlationvalue storage circuit 34 d under the control of the control circuit 40hereinafter described. By repeating this, only those results of thecorrelation calculation carried out for the output signals obtained whenthe spread codes C₁ to C₁₆ are supplied to all of the transmissionconductors 12 which cross an arbitrary one of the reception conductors14, are output to the correlation value storage circuit 34 d. Thecorrelation values of the results of the correlation calculation arestored into predetermined regions of the registers of the correlationvalue storage circuit 34 d.

Similarly, the switches 31 a which form the reception conductorselection circuit 31 and the changeover switch 32 d of the amplificationcircuit 32 are suitably switched so that correlation calculation iscarried out for all output signals obtained from all of the receptionconductors 14 which form the sensor section 100.

Although the correlation value calculation circuit 34 described abovewith reference to FIG. 8 uses a number of correlators 34 b ₁ to 34 b ₁₆equal to the number of the spread codes C_(k) to respectively carry outcorrelation calculation, another configuration is possible where aplurality of correlation value calculation codes C₁′ to C₁₆′ aresuccessively supplied to a single correlator such that correlationcalculation is carried out by the single correlator.

The following describes an example of a correlation value calculationcircuit wherein a plurality of correlation value calculation codes aresuccessively supplied to a single correlator such that the correlatortime-divisionally carries out correlation calculation. FIG. 9 shows anexample of a configuration of the correlation value calculation circuitwhich carries out correlation calculation of spread codestime-divisionally.

A configuration and components of the correlation value calculationcircuit 134 shown in FIG. 9 are described. Referring to FIG. 9, thecorrelation value calculation circuit 134 includes a signal delaycircuit 34 a, a correlator 34 b _(x), a correlation value calculationcode production circuit 134 c _(x), a correlation value storage circuit34 d, and a register 34 e. The register 34 e is provided between outputterminals of the D-flip-flop circuits 34 a ₁ to 34 a ₁₆, which form thesignal delay circuit 34 a, and the correlator 34 b _(x) and temporarilystores output signals PS₁′ to PS₁₆′ of 16 chips output from theD-flip-flop circuits 34 a ₁ to 34 a ₁₆.

The correlator 34 b _(x) carries out correlation calculation between thedata stored in the register 134 e and correlation calculation codesc_(x) supplied from the correlation value calculation code productioncircuit 134 c _(x) to calculate correlation values. An output terminalof the correlator 34 b _(x) is connected to the correlation valuestorage circuit 34 d.

The correlation value calculation code production circuit 134 c _(x)supplies a correlation value calculation code C_(x)′ (PN₁′, PN₂′, PN₃′,. . . , PN₁₅′, PN₁₆′) to the correlator 34 b _(x). The correlation valuecalculation code production circuit 134 c _(x) time-dependently changes(switches) the correlation value calculation code C_(x)′ to be suppliedto the correlator 34 b.

The correlation value storage circuit 34 d is a storage section fortemporarily storing correlation values output from the correlator 34 b_(x). The correlation value storage circuit 34 d is connected to thecorrelator 34 b _(x) and the position detection circuit 35 shown inFIG. 1. The configuration of the other part of the correlation valuestorage circuit 34 d is the same as that of the correlation valuecalculation circuit 34 described hereinabove with reference to FIG. 8,and overlapping description of the same is omitted herein to avoidredundancy.

In the following, operation of the correlation value calculation circuit134 is described in detail. The output signals S₁ to S₁₆ of the I/Vconversion circuits 32 a shown in FIG. 6 are converted into digitalsignals by the A/D conversion circuit 33 and input to the signal delaycircuit 34 a. The digital signals input to the signal delay circuit 34 aare successively supplied to the D-flip-flop circuits 34 a ₁ to 34 a ₁₆connected in series at 16 stages. Then, the D-flip-flop circuits 34 a ₁to 34 a ₁₆ temporarily store the data supplied thereto and output thestored data to the register 134 e. Thereafter, every time a new digitalsignal is supplied, the D-flip-flop circuits 34 a ₁ to 34 a ₁₆ supplydata currently retained therein to the respective adjacent D-flip-flopcircuits 34 a _(x), and store the data newly supplied thereto and outputthe newly supplied data as output signals to the register 134 e.

The correlator 34 b _(x) carries out, if data become complete in theregister 134 e, correlation calculation operation between the datastored in the register 134 e and the correlation value calculation codeC₁′ supplied from the correlation value calculation code productioncircuit 134 c _(x) under the control of the control circuit 40hereinafter described, to calculate a correlation value. Then, thecorrelator 34 b _(x) outputs the correlation value as a result of thecalculation operation to the correlation value storage circuit 34 d.Thereafter, the correlator 34 b _(x) carries out similar correlationcalculation operation also for the correlation value calculation codesC₂′, C₃′, . . . , C₁₆′, respectively, and outputs correlation values asthe results of the calculation operation to the correlation valuestorage circuit 34 d. Thereafter, after the correlator 34 b _(x) carriesout the correlation calculation operation for all correlation valuecalculation codes C₁′ . . . C₁₆′, the data stored in the register 134 eis discarded and the correlator 34 b _(x) waits until the next completedata is stored. Thereafter, the sequence of processes described above isrepeated to carry out the correlation calculation for reception signalsobtained from all of the reception conductors 14 which form the sensorsection 100.

Although the correlation value calculation circuit configured in such amanner as described above with reference to FIG. 9 includes a smallernumber of correlators and correlation value calculation code productioncircuits than the correlation value calculation circuit described abovewith reference to FIG. 8, correlation values of the respective spreadcodes can be obtained similarly as in the case where the same number ofcorrelators are provided as the number of spread codes.

Now, the configuration of the correlator is described in detail withreference to FIG. 10. FIG. 10 shows an example of the configuration ofthe correlators 34 b ₁ to 34 b ₁₆ and 34 b _(x) shown in FIGS. 8 and 9.The correlator 34 b is composed of 16 multipliers 34 f ₁, 34 f ₂, . . ., 34 f ₁₆ and an adder 34 g. The reason why the number of multipliers 34f ₁ to 34 f ₁₆ in the present first embodiment is 16 is that it isintended to determine a correlation of the spread codes C_(k) of 16chips. Accordingly, the number of multipliers differs depending upon thenumber of chips included in each of the spread codes C_(k).

To the multipliers 34 f ₁ to 34 f ₁₆, the chips PS₁ to PS₁₆ of theoutput signal and the chips PN₁′ to PN₁₆′ of the correlation valuecalculation code are supplied, and the signals at the same chippositions are multiplied to obtain multiplication signals. Themultiplication signals calculated by the multipliers 34 f ₁ to 34 f ₁₆are supplied to the adder 34 g. The adder 34 g adds the signals at allchip positions supplied thereto from the multipliers 34 f ₁ to 34 f ₁₆to obtain a correlation value. This correlation value is stored into thecorrelation value storage circuit 34 d. It is to be noted that,depending upon the code to be used, the multipliers 34 f ₁ to 34 f ₁₆may be formed with an adder or a subtracter.

The position detection circuit 35 determines a region of correlationvalues which are higher than a predetermined threshold value, based onthe mapping data stored in the correlation value storage circuit 34 d,and calculates, for example, the central point of the region as theposition of a pointer. Referring to FIG. 1, the position detectioncircuit 35 is connected to the correlation value calculation circuit 34and the control circuit 40. It is to be noted that the positiondetection circuit 35 may include an interpolation circuit forcalculating a coordinate at which a pointer exists, when the pointerexists between two cross points, based on correlation values stored inthe correlation value storage circuit 34 d so that mapping data ofinterpolation values of a higher resolution may be calculated.

The control circuit 40 controls the components of the pointer detectionapparatus 1 according to the present embodiment. Referring to FIG. 1,the control circuit 40 is connected to the clock generation circuit 23,spread code supplying circuit 21, transmission conductor selectioncircuit 22, correlation value calculation circuit 34, and positiondetection circuit 35. The control circuit 40 suitably produces andoutputs a transmission load signal St_(load) (FIG. 11B) and a receptionload signal Sr_(load) (FIG. 11C) based on the clock signal S_(clk) (FIG.11A) output from the clock generation circuit 23, in order to controlthe operation timings of the components.

In the following, operation of the control circuit 40 and the pointerdetection apparatus 1 according to the present first embodiment isdescribed with reference to FIGS. 1, 9 and 11A to 11G. It is to be notedthat, in the following description, it is assumed that the correlationvalue calculation circuit has the configuration of the correlation valuecalculation circuit 134 described hereinabove with reference to FIG. 9in order to facilitate understanding of the principle.

FIG. 11A illustrates a signal waveform of the clock signal S_(clk)supplied from the clock generation circuit 23 to the control circuit 40and the spread code supplying circuit 21. The clock signal S_(clk) has aperiod set to a one-chip length of the spread codes C_(k) for example.FIG. 11B illustrates a signal waveform of the transmission load signalSt_(load) supplied from the control circuit 40 to the transmissionconductor selection circuit 22 and the reception conductor selectioncircuit 31. The transmission load signal St_(load) is a pulse signalwhose period is set, for example, to the code length of the spread codesC_(k), that is, to 16 periods of the clock signal. FIG. 11C illustratesa signal waveform of the reception load signal Sr_(load) supplied fromthe control circuit 40 to the correlation value calculation circuit 34.The reception load signal Sr_(load) is a pulse signal whose period isset, for example, to the code length of the spread codes C_(k), that is,to 16 periods of the clock signal. As illustrated, the reception loadsignal Sr_(load) is output one clock signal S_(clk) period later thanthe transmission load signal St_(load). FIG. 11D illustrates an outputfor transmitting codes from the spread code supplying circuit 21 to thetransmission conductor array 11 shown in FIG. 1. FIG. 11E illustrates anoutput signal of 16 chips set (stored) in the register 134 e through theD-flip-flop circuits 34 a ₁ to 34 a ₁₆, and FIG. 11F illustratesproduction of correlation value calculation codes (C₁′, C₂′, C₃′, . . ., C₁₆′) to be multiplied with the reception signal set in the register134 e.

When the clock signal S_(clk) (FIG. 11A) output from the clockgeneration circuit 23 is input to the control circuit 40 and the spreadcode supplying circuit 21, then the control circuit 40 inputs thetransmission load signal St_(load) (FIG. 11B) to the transmissionconductor selection circuit 22 and the reception conductor selectioncircuit 31 in synchronism with the clock signal S_(clk). After aone-clock period delay, the control circuit 40 inputs the reception loadsignal Sr_(load) to the A/D conversion circuit 33.

The transmission conductor selection circuit 22 starts supply of spreadcodes C_(k) to the transmission conductors 12 at a rising edge timing t₀illustrated in FIG. 11A of the clock signal S_(clk) when thetransmission load signal St_(load) has the high level. Thereafter, thetransmission conductor selection circuit 22 successively switches thetransmission conductors 12 to which the spread codes C_(k) are to besupplied at every rising edge timing such as timings t₂ and t₄ in FIG.11A of the clock signal S_(clk) when the transmission load signalSt_(load) has the high level.

Similarly, the switches 31 a of the reception conductor selectioncircuit 31 select the reception conductors 14 which are to carry outreception first (see FIG. 6) at a rising edge timing of the clock signalS_(clk) when the transmission load signal St_(load) has the high level.Thereafter, the reception conductor selection circuit 31 controls theswitches 31 a to switch the reception conductors 14 to be selected everytime a pulse of the transmission load signal St_(load) is inputsuccessively four times. Here, the reason why the reception conductorselection circuit 31 is set so as to carry out the switching every timea pulse of the transmission load signal St_(load) is input four times isthat, since each transmission block 25 shown in FIG. 4 consists of fourtransmission conductors 12, if the transmission conductors 12 to which aspread code C_(k) is to be supplied are switched at this timing, thenthe spread code C_(k) is supplied to all of the transmission conductors12 which form each transmission block 25. As a result, the spread codesC_(k) are supplied to all of the transmission conductors 12 which formthe sensor section 100.

In such a manner as described above, to the transmission conductors 12selected by the transmission conductor selection circuit 22, the nthchip of each spread code C_(k) is supplied at a rising edge timing ofthe clock signal S_(clk). In particular, at timing t₀, the first chipsof the spread codes C₁ to C₁₆, respectively, are supplied, andthereafter, the chips to be supplied to the transmission conductors 12are switched for every one clock at a rising edge timing of the clockfor the second chip, third chip, and so forth, as seen in FIG. 11D.Then, at a next rising edge timing of the transmission load signalSt_(load), that is, at the 17th rising edge timing of the clock signalS_(clk), the supply of the spread codes C_(k) to the transmissionconductors 12 selected by the transmission conductor selection circuit22 is completed, and consequently, the transmission conductor selectioncircuit 22 switches to the next (adjacent) transmission conductors 12 atthis timing. Thereafter, the transmission conductors are successivelyswitched at each rising edge timing of the transmission load signalSt_(load). In the illustrated example, a one clock period is providedduring which no chip of the spread codes C_(k) is to be supplied priorto the next supplying starting timing of the spread codes C_(k). This isto prevent generation of noise due to a transition phenomenon caused bythe switching operation of the transmission conductor selection circuit22.

Then, after the fourth transmission load signal St_(load) is input tothe transmission conductor selection circuit 22, the transmissionconductor selection circuit 22 returns to the initial state and thenrepeats the sequence of the switching operation described above.

An output signal is output at a rising edge timing of the clock signalS_(clk) from each of the reception conductors 14 selected by thereception conductor selection circuit 31. The reception conductorselection circuit 31 successively switches the reception conductors 14to be selected at the timing of each rising edge of the clock signalS_(clk) when the fifth pulse of the transmission load signal St_(load)has the high level. Then, the reception conductor selection circuit 31returns to the initial state thereof at a rising edge timing of theclock signal S_(clk) when the 33rd pulse of the transmission load signalSt_(load) has the high level, and then repeats the sequence of theswitching operation.

Output signals obtained through the reception conductor selectioncircuit 31 at a rising edge timing of the clock signal S_(clk) areamplified in signal level by the amplification circuit 32, digitallyconverted by the A/D conversion circuit 33, and input to the correlationvalue calculation circuit 134 as seen in FIG. 9. The digital signals aresuccessively input to the D-flip-flops 34 a ₁ to 34 a ₁₆ of the signaldelay circuit 34 a connected to the output terminals of the A/Dconversion circuit 33 beginning with the D-flip-flop 34 a ₁₆ as seen inFIG. 9. The D-flip-flops 34 a ₁ to 34 a ₁₆ store the digital signalsinput from the A/D conversion circuit 33 and supply the stored digitalsignals to the correlators 34 b ₁ to 34 b ₁₆, respectively (FIG. 8) orto the single correlator 34 b _(x) (FIG. 9) provided at the succeedingstage of the D-flip-flops 34 a ₁ to 34 a ₁₆.

In FIG. 9, the transmission signals PS₁′ to PS₁₆′ output from the signaldelay circuit 34 a are set in the register 134 e at a rising edge timingof the clock signal S_(clk) when the transmission load signal St_(load)has the high level. This operation is carried out repetitively withreference to the rising edge timings t₀, t₂, t₄, . . . of the clocksignal S_(clk) (FIG. 11A) when the transmission load signal St_(load)has the high level.

The correlation value calculation circuit 134 causes the correlationvalue calculation code production circuit 134 c _(x) to successivelyproduce 16 different correlation value calculation codes C₁′ to C₁₆′ andsupply the produced correlation value calculation codes C₁′ to C₁₆′ tothe correlator 34 b _(x) at a timing of a rising edge, in FIG. 11A, attime t₃, of the clock signal S_(clk) when the pulse of the receptionload signal Sr_(load) has the high level. At this timing of a risingedge of the clock signal S_(clk) when the reception load signalSr_(load) has the high level, the correlator 34 b _(x) startscorrelation calculation between the correlation value calculation codesC₁′ to C₁₆′ and the signal set in the register 134 e (FIG. 11 (f)). Thecorrelator 34 b _(x) successively outputs the calculation results to thecorrelation value storage circuit 34 d as seen in FIG. 11G. Thereafter,correlation calculation is carried out similarly for the spread codes C₂to C₁₆ and results of the calculation are output to the correlationvalue storage circuit 34 d similarly as seen in FIGS. 11F and 11G. Thecorrelation values are obtained with respect to the correlation valuecalculation codes C₁′ to C₁₆′, respectively, in a manner describedabove.

[Principle of Position Detection]

Now, the principle of position detection of the pointer detectionapparatus 1 according to the present embodiment is described withreference to FIGS. 12A to 16B. As described hereinabove, the pointerdetection apparatus 1 of the present embodiment is an apparatus of thecross point electrostatic coupling system and detects a pointer based ona variation of the electrostatic coupling state of the transmissionconductors and the reception conductors of the sensor section.

First, the detection principle of a pointer is described with referenceto FIGS. 12A and 12B. FIGS. 12A and 12B are sectional views illustratingelectrostatic coupling states between a transmission conductor 12 and areception conductor 14 in a state wherein a pointer 19 such as a fingerdoes not exist on the sensor section 100 (FIG. 12A) and another statewherein a pointer 19 such as a finger exists on the sensor section 100(FIG. 12B), respectively.

Where no pointer 19 exists on the sensor section 100, a transmissionconductor 12 disposed on the first substrate 15 and a receptionconductor 14 disposed on the second substrate 17 are in anelectrostatically coupled state through the spacer 16 as seen in FIG.12A, and an electric field emerging from the transmission conductor 12converges to the reception conductor 14. As a result, all current flowsfrom the transmission conductor 12 to the reception conductor 14. On theother hand, where a pointer 19 exists on the sensor section 100, thetransmission conductor 12 is coupled not only to the reception conductor14 but also to the ground through the pointer 19, as seen in FIG. 12B.In this state, part of the electric field emerging from the transmissionconductor 12 converges to the pointer 19, and part of the currentflowing from the transmission conductor 12 to the reception conductor 14is shunted to the ground through the pointer 19. As a result, thecurrent flowing to the reception conductor 14 decreases. This currentvariation is detected to detect the position pointed to by the pointer19.

Now, a calculation principle of a coordinate of a position pointed by apointer is described with reference to FIGS. 13A to 14B. It is to benoted that attention is paid to a cross point between a transmissionconductor Y₉, to which the spread code C₂ is supplied, and a receptionconductor X₁₂₄, Correlation values obtained depending upon presence andabsence of a pointer 19 at this cross point are described in comparison,so as to explain the coordinate calculation principle. This cross pointis indicated by a blank circle in FIG. 13A, and this cross point ishereinafter referred to simply as “the cross point.” Further, it isassumed that other spread codes (C₁ and C₃ to C₁₆) are supplied from theother transmission conductors 12, which also cross the receptionconductor X₁₂₄, and that the pointer 19 does not exist on or near anycross points other than the cross point (X₁₂₄, Y₉).

First, a correlation value obtained from the reception conductor 14 whenthe pointer 19 does not exist on the sensor section 100 is describedwith reference to FIGS. 13A and 13B. When the pointer 19 does not existon any cross point such as the cross point (X₁₂₄, Y₉), the transmissionconductor 12 is electrostatically coupled only to the receptionconductor 14 (refer to FIG. 12A). As a result, since all of the currentwhich should flow to the reception conductor X₁₂₄ flows to the receptionconductor X₁₂₄, the correlation value obtained by correlationcalculation of the output signal from the reception conductor X₁₂₄exhibits a fixed value in terms of the correlation characteristicbetween the output signal of the correlator and the spread code number(C₂) (see FIG. 13B).

On the other hand, where the pointer 19 exists on the cross point, thetransmission conductor Y₉ is electrostatically coupled to the groundthrough the pointer 19 as seen in FIG. 12B. Consequently, part ofcurrent which should flow to the reception conductor X₁₂₃ is shunted tothe ground through the pointer 19 as seen in FIG. 14A. As a result, ifcorrelation calculation of the output signal from the receptionconductor X₁₂₄ is carried out, then in terms of the correlationcharacteristic between the output signal of the correlator and the codenumber of the spread code, the correlation value obtained with thespread code C₂ is lower than the correlation value obtained bycorrelation calculation with the other spread codes (see FIG. 14B).

Accordingly, the transmission conductor which forms the cross point atwhich the pointer 19 is placed can be specified based on the spread codewhose correlation value is depressed, as illustrated in FIG. 14B. Forexample, in the example illustrated in FIGS. 14A and 14B, since adepression region in which the correlation value is relatively low isproduced at the spread code C₂, it is specified that the transmissionconductor Y₉ to which the spread code C₂ is supplied is the transmissionconductor on which the pointer 19 is placed. Then, the position, thatis, the coordinate, of the pointer 19 on the sensor section 100 can bedetected by specifying the region within which the correlation value islower than a predetermined threshold value, in the spatial distributionof the correlation values stored in the correlation value storagecircuit 34 d.

Now, the principle of position detection where one finger (the pointer19) is placed on a plurality of cross points of the sensor section 100is described with reference to FIGS. 15 to 16B. In the followingdescription, it is assumed that the spread codes C₁ to C₁₆ are suppliedto the transmission conductors Y₁ to Y₆₄ (see FIG. 4) and one finger(the pointer 19) is placed on a plurality of cross points between thereception conductor X₁₂₄ and the transmission conductors Y₁ to Y₄ asseen in FIG. 15. It is to be noted that the spread code C₁ is suppliedto the transmission conductors Y₁ to Y₄ on which the pointer 19 isplaced.

In the state illustrated in FIG. 15, current flowing into the receptionconductor X₁₂₄ decreases at a plurality of cross points formed betweenthe reception conductor X₁₂₄ and the transmission conductors Y₁ to Y₄.Accordingly, as seen in FIG. 16A, the correlation characteristic 64between the output signal of the correlator for the reception conductorX₁₂₄ and the code number of the spread code C₁ is lower than thecorrelation values obtained by correlation calculation with regard tothe other spread codes. The characteristic is the same as illustrated inFIG. 16A when the spread code C₁ is supplied to the multipletransmission conductors Y₂ to Y₄.

On the other hand, the pointer 19 does not exist at a plurality of crosspoints formed between the reception conductor X₁₂₄ and the transmissionconductors Y₅ to Y₆₄. Accordingly, as seen in FIG. 16B, the correlationcharacteristic 65 for Y₅ to Y₆₄ becomes constant.

In this manner, with the pointer detection apparatus 1 of the presentembodiment, even when a pointer is placed at a plurality cross points,both the presence and position of the pointer can be detected. It is tobe noted that, if an interpolation processing circuit is provided in theposition detection circuit 35 described hereinabove, then since thepresence or absence of the pointer 19 between cross points can bedetected, it is also possible to estimate the shape of the pointer 19placed on the sensor section 100.

[Example of the Hadamard Code]

In the first embodiment described above, the spread codes C_(k) having acode length of 2n chips are supplied as a signal to be supplied to thesensor section 100. As the spread codes C_(k), Hadamard codes may beused. An example wherein the Hadamard codes are used is described withreference to FIGS. 17A and 17B.

FIG. 17A illustrates an Hadamard matrix which includes code strings C₁to C₁₆ having the length of 16 chips. The value of each of the chipswhich form the code strings C₁ to C₁₆ is −1 or +1. The code strings C₁to C₁₆ are hereinafter referred to as Hadamard codes.

In the Hadamard matrix, since the 16 Hadamard codes C₁ to C₁₆ have afully orthogonal relationship to each other, the Hadamard codes C₁ toC₁₆ and the correlation value calculation codes C₁′ to C₁₆′ can be madethe same codes, respectively. Further, for the correlator for carryingout correlation calculation, an adder/subtracter can be used in place ofthe multipliers 34 f ₁ to 34 f ₁₆ described hereinabove with referenceto FIG. 10. Further, where the Hadamard matrix is used, and if it isdetected by the correlator that there is a correlation, then thecorrelation value of an Hadamard code C_(x) having such correlationdrops as seen in FIG. 17C, resulting in detection of presence of acorrelation at the corresponding code. However, even where there is acorrelation, the level of the correlation value is higher than the 0level.

Where the Hadamard matrix of FIG. 17A is used in the pointer detectionapparatus of the present invention, since all of the Hadamard codes C₁to C₁₆ which form the Hadamard matrix exhibit 1 at the first chip, ifcorrelation calculation at this chip position is carried out by thecorrelator, then the correlation value may become excessively high.Therefore, in the example of FIG. 17B, the Hadamard codes are composedof 15 chips. The 16 different Hadamard codes C₁ to C₁₆ formed from 15chips are equivalent, as can be recognized from the comparison with FIG.17A, to those of FIG. 17A from which the first chip of each of theHadamard codes of 16 chips is removed.

Where the 16 different Hadamard codes C₁ to C₁₆ formed from 15 chipsillustrated in FIG. 17B are used, the output signal of the correlatorhas a level lower than the 0 level when a correlation exists whereas,where there is no correlation, the output signal of the correlatorexhibits a predetermined level higher than the 0 level as seen in FIG.17D. Consequently, beat can be reduced.

[Processing Procedure of Position Detection]

Now, operation of the pointer detection apparatus 1 according to thefirst embodiment is described with reference to FIGS. 1 and 6 as well asa flow chart of FIG. 18.

First, the spread code production circuits 24 of the spread codesupplying circuit 21 respectively produce the spread codes C₁ to C₁₆ atstep S1. Then, the reception conductor selection circuit 31 of thereception section 300 connects predetermined ones of the receptionconductors 14 in the respective detection blocks 36 and the I/Vconversion circuits 32 a by means of the switches 31 a at step S2.

Then, the transmission conductor selection circuit 22 selectspredetermined ones of the transmission conductor 12 to which the spreadcodes C₁ to C₁₆ are to be supplied in the respective transmission blocks25 at step S3. Then at step S4, the spread codes C₁ to C₁₆ are suppliedto the predetermined transmission conductors 12 selected in thetransmission blocks 25.

Then at step S5, the reception section 300 simultaneously detects theoutput signals S₁ from the predetermined reception conductors 14 in thedetection blocks 36 selected at step S2. In particular, theamplification circuit 32 first converts current signals output from theselected predetermined reception conductors 14 (i.e., total 16 receptionconductors 14 in the illustrated embodiment) into voltage signals andamplifies the voltage signals by means of the I/V conversion circuits 32a, and then outputs the amplified signals to the A/D conversion circuit33. Then, the A/D conversion circuit 33 converts the voltage signalsinput thereto into digital signals and outputs the digital signals tothe correlation value calculation circuit 34.

Then, the correlation value calculation circuit 34 carries outcorrelation calculation of the input digital signals with regard to thecorrelation value calculation codes C₁′ to C₁₆′ and stores resultingvalues in the correlation value storage circuit 34 d at step S6.

Then, the control circuit 40 decides at step S7 whether or not thecorrelation calculation is completed with regard to all of thetransmission conductors 12 on the reception conductor 14 selected atstep S4. If the position detection with regard to all of thetransmission conductors 12 on the selected reception conductor 14 is notcompleted, that is, if the result of decision at step S7 is NO, then theprocessing returns to step S3. At step S3, the switches 22 a of thetransmission blocks 25 in the transmission conductor selection circuit22 are switched to select the transmission conductors 12 different fromthose in the preceding operation cycle and, thereafter the processes atsteps S3 through S6 are repeated. Thereafter, the processes at steps S3through S6 are repeated until the position detection with regard to allof the transmission conductors 12 on the selected reception conductor 14is completed.

In particular, if it is assumed that the reception conductors X₁, X₉, .. . , X₁₂₁ are selected first as seen in FIG. 6, then the spread codesC₁ to C₁₆ are first supplied to the transmission conductors Y₄, Y₈, . .. , Y₆₄, respectively. Then, while the selected reception conductorsremain selected, the transmission conductors to which the spread codesC₁ to C₁₆ are to be supplied are switched to the transmission conductorsY₃, Y₇, . . . , Y₆₃ and the spread codes C₁ to C₁₅ are supplied to thetransmission conductors Y₃, Y₇, . . . , Y₆₃ so that correlationcalculation is carried out. If this process is repeated until the spreadcodes C₁ to C₁₆ are supplied to the transmission conductors Y₁, Y₅, . .. , Y₆₁ to carry out correlation calculation, then one cycle of theswitching of the transmission conductors 12 in each of the transmissionblocks 25 is completed and the position detection of all of thetransmission conductors 12 with regard to the reception conductors X₁,X₉, . . . , X₁₂₁ is completed. This is decided as a state of YES at stepS7. If the detection of all of the transmission conductors 12 on theselected reception conductor(s) 14 is completed in this manner, then theprocessing advances to step S8.

Where the correlation calculation with regard to all of the transmissionconductors 12 on the reception conductor 14 selected at step S2 iscompleted, that is, where the result of decision at step S7 is YES, thecontrol circuit 40 decides whether or not the position detection on allof the reception conductors 14 is completed at step S8. If thecorrelation calculation on all of the reception conductors 14 is notcompleted, that is, if the result of decision at step S8 is NO, then theprocessing returns to step S2, at which the switches 31 a in thereception conductor selection circuit 31 are switched to select thereception conductors 14. At step s3, the switches 221 in thetransmission conductor selection circuit 22 are controlled to selectpredetermined transmission conductors 12. Then, in step s4, the spreadcodes C₁ to C₁₆ are supplied at the same time to the selected pluraltransmission conductors 12 from the spread code supplying circuit 21. Inthis manner, the transmission conductors 12 and the reception conductors14 are selectively switched to continue the correlation calculation.Thereafter, the processes at steps S2 to S7 are repeated until thecorrelation calculation with regard to all of the transmissionconductors 12 on all reception conductors 14 is completed. This isdecided as a state of YES at step S8.

In short, the transmission conductors 12 in the transmission blocks 25are rotated in a state wherein, for example, the reception conductorsX₁, X₉, . . . , X₁₂₁ are selected as seen in FIG. 6 to carry outcorrelation calculation with regard to all of the transmissionconductors 12 on the reception conductors X₁, X₉, . . . , X₁₂₁.Thereafter, the reception conductors are switched to the receptionconductors X₂, X₁₀, . . . , X₁₂₂ and the transmission conductors 12 inthe transmission blocks 25 are again rotated. This process is repeatedto successively switch between the reception conductors 14. Then, if thecorrelation calculation is completed on the last set of the receptionconductors X₈, X₁₆, . . . , X₁₂₈ at the end of the rotation, then theprocessing advances to step S9, but otherwise, the processing returns tothe step S2.

The position detection circuit 35 detects, based on signals at the crosspoints of the reception conductors 14 stored in the correlation valuestorage circuit 34 d of the correlation value calculation circuit 34,from which reception conductor(s) 14 a reduced-level signal is outputand further detects the corresponding spread code. Then at step S9, theposition detection circuit 35 calculates the position of the pointerbased on the index m (1 to 128) of the reception conductor 14 specifiedfrom the signal level and the index n (1 to 64) of the transmissionconductor 12 from which the corresponding spread code is supplied. Theposition detection of the pointer disposed on the sensor section 100 iscarried out in this manner.

In the present first embodiment, different spread codes are supplied topredetermined ones of the transmission conductors 12 in the respectivegroups at the same time, that is, multiplex-transmitted, to detect theposition of the pointer simultaneously by means of predetermined pluralones of the reception conductors 14. In other words, a simultaneousdetection process is carried out at the same time for a plurality ofcross points between the transmission conductors 12 and the receptionconductors 14. As a result, the time required for position detection ofa plurality of cross points can be reduced, and such position detectionof the pointer can be carried out at a higher speed.

In particular, since, in the first embodiment, the transmissionconductor array 11 and the reception conductor array 13 are individuallydivided into 16 groups which are processed in parallel to each other,the detection time of the transmission conductor array 11 and thereception conductor array 13 can be reduced to 1/(16×16) in comparisonwith the detection time required for successively carrying out adetection process for all cross points as in the prior art. It is to benoted that the number of groups is not limited to the specific numberdescribed above. Naturally, detection time reduction can be achievedalso where only one of the transmission conductor array 11 and thereception conductor array 13 is divided into groups.

Since the pointer detection apparatus of the present invention makes itpossible to detect a pointer at a plurality of cross pointssimultaneously and at a high speed as described above, it is possiblenot only to detect a plurality of pointed positions by differentpointers of one user at a high speed, but also to detect a plurality ofpointed positions by different pointers of a plurality of users at thesame time. Since a plurality of pointers can be detected at the sametime irrespective of the number of users, the pointer detectionapparatus can contribute to development of various applications. It isto be noted that, since it is possible to detect a plurality of pointersat the same time, naturally it is possible to detect pointing by asingle pointer.

While the first embodiment described above is configured such that,after detection with regard to all transmission conductors on onereception conductor is completed, the reception conductor for suchdetection is switched to another (e.g., adjacent) reception conductor torepeat the position detection, the present invention is not limited tothis configuration. For example, the reception conductor for detectionmay be switched to another reception conductor to continue the positiondetection before the detection with regard to all transmissionconductors on one reception conductor is completed, as long as positiondetection at all cross points of the sensor section 100 is completedfinally.

Further, while, in the first embodiment described above, the position ofa pointer is detected, the present invention is not limited to thisconfiguration. For example, it is possible to use the pointer detectionapparatus according to the first embodiment as an apparatus fordetecting only the presence or absence of a pointer from correlationvalues obtained by the pointer detection apparatus. It is to be notedthat, in this case, the position detection circuit 35 does not have tobe provided.

2. Second Embodiment Examples of a Configuration Which Uses aPSK-Modulated Spread Code

While, in the first embodiment described above, the spread codes C_(k)are supplied directly to the transmission conductor array 11, thepresent invention is not limited to this configuration. For example, thespread codes C_(k) may be supplied to the transmission conductor array11 after predetermined modulation is applied thereto. The secondembodiment is directed to an example of a configuration wherein thespread codes C_(k) to be supplied to the transmission conductor array 11are PSK (Phase Shift Keying) modulated.

[PSK Modulation]

FIGS. 19A and 19B illustrate waveforms of spread codes before and afterPSK modulation. In particular, FIG. 19A illustrates a waveform of aspread code before PSK modulation and FIG. 19B illustrates a waveform ofthe spread code after the PSK modulation.

In the present second embodiment, the spread codes C_(k) are PSKmodulated with a signal having a clock period equal to half the clockperiod of the spread codes C_(k) (i.e., chip period), for example. It isto be noted that the present invention is not limited to thisconfiguration, and the ratio between the clock period for modulation andthe clock period before modulation (i.e., chip period) may be changedsuitably in accordance with each application. In the present PSKmodulation, for example, when the signal level of the spread codesbefore modulation illustrated in FIG. 19B is High, the signal isreversed at a timing at which the signal level begins with the Lowlevel, but when the signal level is Low, the signal is reversed atanother timing at which the signal level begins with the High level. Asa result, the modulation signal illustrated in FIG. 19B is obtained.

[Configuration of the Pointer Detection Apparatus]

A pointer detection apparatus 2 according to the second embodiment isdescribed with reference to FIG. 20. The pointer detection apparatus 2of the second embodiment includes a sensor section 100, a transmissionsection 201, a reception section 301, and a control circuit 40. Thepointer detection apparatus 2 according to the present second embodimentis different from the pointer detection apparatus 1 according to thefirst embodiment described hereinabove with reference to FIG. 1 in thatthe transmission section 201 includes a spread code supplying circuit221, which in turn includes a PSK modulation circuit for applying PSKmodulation to the spread codes C_(k), and that the reception section 301includes a correlation value calculation circuit 304, which in turnincludes a PSK demodulation circuit for demodulating the PSK-modulatedspread codes C_(k). The pointer detection apparatus 2 according to thepresent second embodiment is similar in configuration of the remainingpart to the pointer detection apparatus 1 according to the firstembodiment described hereinabove with reference to FIG. 1, andtherefore, overlapping description of the remaining part of the pointerdetection apparatus 2 is omitted herein to avoid redundancy. It is to benoted that, in the present second embodiment, the spread codes C_(k)have, for example, a 63-chip length and PSK modulation is applied usinga clock signal having half the period of the spread codes C_(k) (i.e.,the chip period) to produce a modulated signal of a 126-clock length.

Now, a configuration of the transmission section 201 in the secondembodiment is described with reference to FIG. 21. A spread codesupplying circuit 221 includes a plurality of spread code productioncircuits 24 and a plurality of PSK modulation circuits 26. The PSKmodulation circuits 26 are provided at output terminals of the spreadcode production circuits 24 since they respectively PSK-modulate 16different spread codes C₁, C₂, . . . , C₁₆ produced in synchronism witheach other based on the same clock supplied from the clock generationcircuit 23. In particular, the number of PSK modulation circuits 26 isequal to the number of spread code production circuits 24, that is, 16.The PSK modulation circuits 26 PSK-modulate the spread codes C₁, C₂, . .. , C₁₆ to produce 16 different PSK modulation signals C_(1P), C_(2P), .. . , C_(16P). The PSK modulation signals C_(1P) to C_(16P) are suppliedto the transmission conductors 12.

A configuration of the correlation value calculation circuit 304 in thepresent second embodiment is described with reference to FIG. 22. FIG.22 shows a circuit configuration of the correlation value calculationcircuit 304 in the second embodiment and a connection scheme of thecorrelation value calculation circuit 304, the I/V conversion circuit 32a, and the A/D conversion circuit 33.

The correlation value calculation circuit 304 includes a PSKdemodulation circuit 126, a signal delay circuit 304 a, 16 correlators304 b ₁, 304 b ₂, 304 b ₃, . . . , 304 b ₁₆, 16 correlation valuecalculation code production circuits 304 c ₁ to 304 c ₁₆, and acorrelation value storage circuit 304 d.

The signal delay circuit 304 a temporarily retains digital signalssuccessively input thereto from the A/D conversion circuit 33 andsimultaneously supplies the retained data to the correlators 304 b ₁ to304 b ₁₆ similarly to the signal delay circuit 34 a in the firstembodiment described above. The signal delay circuit 304 a includes anumber of D-flip-flop circuits 304 a ₁, 304 a ₂, 304 a ₃, . . . , 304 a₆₂, 304 a ₆₃ equal to the number of the code length of the spread code,which is 63. The D-flip-flop circuits 304 a ₆₂, 304 a ₆₂, 304 a ₆₁, . .. , 304 a ₃, 304 a ₂, 304 a ₁ are connected in series in this order fromthe A/D conversion circuit 33 side. An output terminal of each of theD-flip-flop circuits 304 a ₁ to 304 a ₆₃ is connected to a neighboringone of the D-flip-flop circuits 304 a ₆₃ to 304 a ₂ (for example, theoutput terminal of the D-flip-flop circuit 304 a ₆₃ is connected to theD-flip-flop circuit 304 a ₆₂) and also to the correlators 304 b ₁ to 304b ₁₆. Output signals from the D-flip-flop circuits 304 a ₁ to 304 a ₆₃are input to all of the correlators 304 b ₁ to 304 b ₁₆.

The PSK demodulation circuit 126 demodulates the spread codes that werePSK-modulated by the PSK modulation circuit 26 of the transmissionsection 201 shown in FIG. 21 back into the original spread codes C_(k).As seen in FIG. 22, the PSK demodulation circuit 126 is interposedbetween the A/D conversion circuit 33 and the signal delay circuit 304a, and PSK-demodulates the output signals digitally converted by the A/Dconversion circuit 33 to output the PSK demodulated signals to thesignal delay circuit 304 a at the following stage. In particular, thePSK demodulation circuit 126 demodulates PSK modulation signals intosignals prior to the modulation illustrated in FIG. 19A, that is, intothe original spread codes C_(k). It is to be noted that, while, in thepresent second embodiment, the PSK demodulation circuit 126 is providedin the correlation value calculation circuit 304, that is, the PSKdemodulation circuit 126 demodulates the output signals after beingconverted into digital signals, the present invention is not limited tothis configuration. Since PSK demodulation can be applied to any signalsafter conversion of current signals of the output signals into voltagesignals, the PSK demodulation circuit 126 may otherwise be providedbetween the amplification circuit 32 (I/V conversion circuits 32 a) andthe A/D conversion circuit 33.

The output signals demodulated by the PSK demodulation circuit 126 aresupplied to the D-flip-flop circuits 304 a ₁ to 304 a ₆₃ connected inseries at a plurality of stages. In the following description, theoutput signals of 63 chips output from the 63 D-flip-flop circuits 304 a₁ to 304 a ₆₃ are referred to as output signals PS₁, PS₂, PS₃, . . . ,PS₆₂, PS₆₃.

The output signals PS₁ to PS₆₃ of 63 chips are supplied at the same timeto the 16 correlators 304 b ₁ to 304 b ₁₆. The correlators 304 b ₁ to304 b ₁₆ carry out correlation calculation between the output signalsPS₁ to PS₆₃ of 63 chips and the correlation value calculation codes C₁′to C₁₆′ supplied from the correlation value calculation code productioncircuits 304 c ₁ to 304 c ₁₆, respectively, to calculate correlationvalues. In particular, for example, the correlator 304 b ₁ is suppliedwith the correlation value calculation code C_(1P)′ (PN₁′ to PN₆₃′) of63 chips from the correlation value calculation code production circuit304 c ₁, carries out correlation calculation of the output signal andthe correlation value calculation code for each chip and supplies thecorrelation value between them to the correlation value storage circuit304 d to carry out correlation detection of the spread code C₁.

Similarly, the correlators 304 b ₂ to 304 b ₁₆ carry out correlationcalculation between the output signals PS₁ to PS₆₃ and the correlationvalue calculation codes C_(2P)′ to C_(16P)′ and supply correlationvalues that result from the calculation to the correlation value storagecircuit 304 d to be stored therein. In this manner, the correlationcalculation is carried out respectively for all of the 16 spread codesand resulting correlation values are stored into the correlation valuestorage circuit 304 d. It is to be noted that, while the configurationshown in FIG. 22 uses a number of correlators corresponding to thenumber of different spread codes, the present invention is not limitedto this configuration. For example, another configuration may be appliedwherein the configuration described hereinabove with reference to FIG. 9is applied to the correlation value calculation circuit 304 and thecorrelation value calculation circuit is formed from a single correlatorand a correlation value calculation code production circuit which cansupply a plurality of correlation value calculation codes such that aplurality of different correlation values are calculatedtime-divisionally.

As described above, in the present second embodiment, spread codesdifferent from each other are PSK modulated, and the PSK-modulatedspread codes are supplied at the same time or multiplex-transmitted tothe transmission conductors which form the transmission conductor groupsuch that the position of a pointer is determined at the same time by aplurality of selected reception conductors. As a result, with thepresent second embodiment, similar effects as of the first embodimentcan be achieved.

Further, in the present second embodiment, when spread codes to besupplied to the transmission conductors are to be PSK modulated, a clocksignal of a period shorter than the chip period of the spread codes isused. In this instance, when the spread codes are demodulated by thereception section, the frequency of signal transition at a rising edgeand a falling edge of the demodulated spread codes can be increased.Therefore, in the present second embodiment, the error in positiondetection of a pointer can be reduced. Further, by PSK-modulating spreadcodes, the noise resisting property can be improved.

While, in the present second embodiment, PSK-modulated spread codes aresupplied to the transmission conductors, the present invention is notlimited to this configuration. In a third embodiment described below,spread codes are modulated in a different manner before they aresupplied.

3. Third Embodiment Examples of a Configuration Which Uses anFSK-Modulated Spread Code

The third embodiment is configured such that the spread codes C_(k) tobe supplied to the transmission conductor array 11 are FSK (FrequencyShift Keying) modulated.

[FSK Modulation]

FIGS. 23A and 23B illustrate waveforms of spread codes before and afterFSK modulation, respectively.

In the third embodiment described below, a signal of a clock frequencyequal to, for example, twice or four times the clock frequency of thespread codes C_(k) before modulation (i.e., the chip rate) is used forFSK modulation. It is to be noted that the present invention is notlimited to this configuration and the ratio between the clock frequencyfor modulation and the chip rate can be changed suitably according toeach application or the like. In the FSK modulation in the present thirdembodiment, a signal of a High level state in the spread codes beforemodulation illustrated in FIG. 23A corresponds to a signal of afrequency that is four times that of the spread codes before modulation,while a signal in a Low level state corresponds to a signal of afrequency that is twice that of the spread codes before modulation, toobtain a modulation signal illustrated in FIG. 23B. Also in the presentthird embodiment, spread codes of a 63-chip length are used similarly asin the second embodiment described above, and signals of clockfrequencies of twice and four-times are used to apply FSK modulation tothe spread codes to produce an FSK modulation signal. It is to be notedthat, if the configuration of the pointer detection apparatus accordingto the present third embodiment is compared with that of the pointerdetection apparatus 2 of the second embodiment described hereinabove,then the former is the same as the latter except that the spread codesupplying circuit 221 and the correlation value calculation circuit 304are replaced with the spread code supplying circuit 222 and thecorrelation value calculation circuit 314, respectively. Therefore, likeelements are denoted by like reference characters and overlappingdescription of them is omitted herein to avoid redundancy.

First, a configuration of a spread code supplying circuit 222 in thepresent third embodiment is described with reference to FIG. 24. Thespread code supplying circuit 222 includes a plurality of spread codeproduction circuits 24 and a plurality of FSK modulation circuits 27. Inthe present embodiment, in order to FSK-modulate 16 different spreadcodes C₁, C₂, . . . , C₁₆ produced in synchronism with each other basedon the same clock, 16 spread code production circuits 24 and 16 FSKmodulation circuits 27 are provided. The FSK modulation circuits 27FSK-modulate the spread codes C₁ to C₁₆ and supply FSK modulationsignals C_(1F), C_(2F), . . . , C_(16F) to the transmission conductors12, respectively.

A configuration of a correlation value calculation circuit 314 in thepresent third embodiment is described with reference to FIG. 25. FIG. 25shows a circuit configuration of the correlation value calculationcircuit 314 in the third embodiment and a connection scheme of thecorrelation value calculation circuit, the I/V conversion circuit 32 a,and the A/D conversion circuit 33.

The correlation value calculation circuit 314 includes an FSKdemodulation circuit 127, a signal delay circuit 304 a, 16 correlators304 b ₁, 304 b ₂, . . . , 304 b ₁₆, a number of correlation valuecalculation code production circuits 304 c ₁, 304C₂, . . . , 304 c ₁₆equal to the number of the correlators 304 b ₁ to 304 b ₁₆, that is, 16correlation value calculation code production circuits 304 c ₁, 304C₂, .. . , 304 c ₁₆, and a correlation value storage circuit 304 d.

The FSK demodulation circuit 127 demodulates spread codes that wereFSK-modulated by the FSK demodulation circuit 27 shown in FIG. 24 backinto the original spread codes. The FSK demodulation circuit 127 isinterposed between the A/D conversion circuit 33 and the signal delaycircuit 304 a, and FSK-demodulates the output signals that are digitallyconverted by the A/D conversion circuit 33. In particular, the FSKdemodulation circuit 127 demodulates signals modulated, for example, inthe state illustrated in FIG. 23B so that the demodulated signals havethe same state as that of the signals before modulation as illustratedin FIG. 23A. It is to be noted that, while, in the present thirdembodiment, the FSK demodulation circuit 127 is provided in thecorrelation value calculation circuit 314, that is, the FSK demodulationcircuit 127 demodulates the output signals converted into digitalsignals, the present invention is not limited to this configuration.Since signals obtained by converting current signals into voltagesignals can be FSK-demodulated, the FSK demodulation circuit 127 mayotherwise be provided between the I/V conversion circuit 32 a and theA/D conversion circuit 33.

The output signals demodulated by the FSK demodulation circuit 127 aresupplied to the D-flip-flop circuits 304 a ₁ to 304 a ₆₃ connected inseries at a plurality of stages, and the output signals from theD-flip-flop circuits 304 a ₁ to 304 a ₆₃ are input to all correlators304 b ₁ to 304 b ₁₆. It is to be noted that, since the configuration andthe process of the other part of the correlation value calculationcircuit 314 are the same as those of the second embodiment describedhereinabove with reference to FIG. 22, overlapping description of themis omitted herein to avoid redundancy.

In the present embodiment, a plurality of spread codes are FSKmodulated, and the FSK-modulated spread codes are supplied at the sametime, that is, multiplex-modulated, to a plurality of transmissionconductors 12 which form the transmission conductor array 11 such thatthe position of a pointer is detected at the same time by a plurality ofselected reception conductors 14. As a result, in the present thirdembodiment also, similar effects as in the second embodiment can beachieved.

Further, by FSK-modulating spread codes, the bandwidth of signals to besupplied to the transmission conductor array 11 can be widened, andconsequently, the noise resisting property can be improved.

4. Fourth Embodiment Different Supplying Methods of a Spread Code

The first embodiment described hereinabove with reference to FIG. 4 isconfigured such that the transmission conductors 12 which form thetransmission conductor array 11 are divided into a plurality oftransmission blocks 25 each composed of four transmission conductorsY_(n) to Y_(n+3) positioned adjacent to each other, and the spread codesC₁ to C₁₆ are supplied respectively to the plural transmission blocks 25while each of the spread codes C₁ to C₁₆ is supplied to one of the fourtransmission conductors Y_(n) to Y_(n+3) forming each of thetransmission blocks 25. However, according to the present invention, thespread codes C₁ to C₁₆ need not be supplied to predetermined ones of thetransmission conductors 12 and may be suitably supplied to arbitraryones of the transmission conductors 12.

In the following, modifications 1 to 3 to the supplying method of spreadcodes are described with reference to FIGS. 26 to 29.

[Modification 1]

First, the supplying method of spread codes according to themodification 1 is described with reference to FIG. 26. In the presentmodification 1, though not particularly shown, for example, a switch isprovided between the transmission conductor selection circuit 22 and thespread code supplying circuit 21 shown in FIG. 4. The switch isconfigured such that the spread codes C₁ to C₁₆ supplied from the spreadcode supplying circuit 21 are selectively supplied to the transmissionconductor selection circuit 22 through the switch (not shown). It is tobe noted that the other part of the modification 1 has the sameconfiguration as that of the first embodiment described hereinabove withreference to FIG. 1, and therefore FIG. 1 is referred to whereappropriate while description of the common configuration is omittedherein.

The transmission conductor selection circuit 22 selects 16 transmissionconductors 12 at intervals of four transmission conductors 12 from amongthe transmission conductors Y₁ to Y₆₃. In particular, the transmissionconductor selection circuit 22 first selects the transmission conductorsY₁, Y₅, . . . , Y₅₇, Y₆₁ and supplies the spread codes C₁ to C₁₆ to theselected transmission conductors 12. Then, in this state, supply of thespread codes can be carried out for a predetermined period of time.

Thereafter, the transmission conductor selection circuit 22 selects thetransmission conductors 12 at positions displaced by a one-conductordistance in a direction in which the index n of the transmissionconductor 12 increases. In particular, the 16 transmission conductorsY₁, Y₅, . . . , Y₅₇, Y₆₁ selected in the preceding cycle are changed(switched) to the transmission conductors Y₂, Y₆, . . . , Y₅₈, Y₆₂,respectively. Then, the spread codes C₁ to C₁₆ supplied from the spreadcode supplying circuit 21 are supplied at the same time to the newlyselected transmission conductors Y₂, Y₆, . . . , Y₅₈, Y₆₂, respectively.Thereafter, the switching operation of the transmission conductors 12described above is successively repeated to carry out supply of thespread codes.

Then, after the spread codes C₁ to C₁₆ are supplied at the same time tothe transmission conductors Y₄, Y₈, . . . , Y₆₀, Y₆₄ by the transmissionconductor selection circuit 22, then those transmission blocks 25 shownin FIG. 4 to which the spread codes are to be supplied are changed(switched) by the switch (not shown) and then the operation describedabove is repeated. For example, if attention is paid to the transmissionblock 25 which consists of the transmission conductors Y₁ to Y₄, thenthe spread code C₁ is supplied first to the transmission block 25 andsupply of the spread code C₁ is carried out to the transmissionconductors 12 beginning with the transmission conductor Y₁. Then, thetransmission conductor selection circuit 22 successively switches thetransmission conductor 12 to which the spread code C₁ is to be supplied,as described above. Then, after the spread code C₁ is supplied to thetransmission conductor Y₄, the transmission conductor selection circuit22 switches the transmission conductor 12 to which the spread code is tobe supplied to the transmission conductor Y₁, and the switch (not shown)changes the spread code to be supplied to the transmission block 25 tothe spread code C₁₆ and then repeats the switching operation describedabove. After the spread code is supplied to the transmission conductorY₄ again, the transmission conductor selection circuit 22 again switchesthe transmission conductor to which the spread code is to be supplied tothe transmission conductor Y₁ and the switch (not shown) changes thespread code to the spread code C₁₅ and, thereafter the operationdescribed above is repeated.

It is to be noted that, although, in the example described above as themodification 1, the transmission conductor selection circuit 22 switchesthe transmission conductor 12 to be connected in a direction in whichthe index n of the transmission conductor 12 increases after everypredetermined interval of time, the present invention is not limited tothis configuration. For example, the transmission conductor 12 to beconnected to the spread code supplying circuit 21 may be switched in adirection in which the index n thereof decreases. Further, thetransmission conductor 12 may be switched at random in accordance with apredetermined sequence. Further, while the foregoing description isdirected to switching of the transmission conductor 12, likewise, thereception conductors 14 may be switched at random in accordance with apredetermined sequence.

[Modification 2]

In the modification 1, the transmission conductor selection circuit 22selects 16 transmission conductors 12 at four conductor intervals fromamong the transmission conductors Y₁ to Y₆₄ after every predeterminedinterval of time, and switches the selected transmission conductors 12in a direction in which the index n of the transmission conductor 12increases to supply the spread codes C_(k) thereto. However, theselection of the transmission conductors 12 to which the spread codesC_(k) are to be supplied need not be carried out at intervals of apredetermined number of conductors.

The modification 2 is described with reference to FIGS. 27 and 28.First, a configuration of a transmission conductor selection circuit 202in the modification 2 is described with reference to FIG. 27. In thepresent modification 2, the transmission conductor array 11 is dividedinto a plurality of transmission blocks 125 each including 16transmission conductors Y_(n) to Y_(n+15) which are positioned adjacentto each other. In particular, the transmission conductor array 11including 64 transmission conductors Y₁ to Y₆₄ is divided into fourtransmission blocks, which respectively include the transmissionconductors Y₁ to Y₁₆, Y₁₇ to Y₃₂, Y₃₃ to Y₄₈, and Y₄₉ to Y₆₄.

The transmission conductor selection circuit 202 includes a switch 202 afor supplying the spread codes C₁ to C₁₆ output from the spread codesupplying circuit 21 to the individual transmission blocks 125.

The switch 202 a is formed as a switch group including 16 switches, andoutput terminals 202 b of the 16 switches are connected to correspondingtransmission conductors Y_(n) to Y_(n+15) while input terminals 202 c ofthe 16 switches are connected to the corresponding spread codeproduction circuits 24 of the spread code supplying circuit 21 as shownin FIGS. 1 and 3. Then, the switch 202 a time-dependently switchesbetween the transmission blocks 125 to be connected to the spread codeproduction circuits 24 such that the spread codes C₁ to C₁₆ can besupplied to all transmission conductors 12. It is to be noted that, inFIG. 27, the switch 202 a is shown in a simplified form to avoid unduecomplexity. Further, the configuration of the other part of thetransmission conductor selection circuit is the same as that of thefirst embodiment described hereinabove with reference to FIG. 1 andoverlapping description of the same is omitted herein to avoidredundancy.

A supplying method of spread codes in the modification 2 is describedwith reference to FIG. 28. First, the transmission conductor selectioncircuit 202 selects the transmission block 125 which includes thetransmission conductors Y₁ to Y₁₆ as seen in FIG. 28. Then, the spreadcode supplying circuit 21 supplies the spread codes C₁ to C₁₆ at thesame time to the transmission conductors Y₁ to Y₁₆, respectively, whichform the selected transmission block 125. In this state, supply of thespread codes C₁ to C₁₆ is carried out for a predetermined period oftime. Then, the transmission conductor selection circuit 202 switchesover to the transmission block 125 which includes the transmissionconductors Y₁₇ to Y₃₂ to be connected to the spread code supplyingcircuit 21, and supplies the spread codes C₁ to C₁₆ at the same time tothe transmission conductors Y₁₇ to Y₃₂, respectively. Thereafter, thetransmission conductor selection circuit 202 repeats the operation ofswitching over to the next transmission block 125 and the operation ofsupplying the spread codes C₁ to C₁₆ at the same time to the newlyselected transmission block. Then, after the transmission conductorselection circuit 202 selects the transmission block 125 which includesthe transmission conductors Y₄₉ to Y₆₄ and completes supplying thespread codes C₁ to C₁₆ from the spread code supplying circuit 21 to thetransmission conductors Y₄₉ to Y₆₄, the transmission conductor selectioncircuit 202 returns to the transmission block 125 which includes thetransmission conductors Y₁ to Y₁₆ and repeats the switching operationand the spread code supplying operation.

[Modification 3]

In the modification 2 described above, the transmission blocks 125 areused each including 16 transmission conductors Y_(n) to Y_(n+15) thatare positioned adjacent to each other, and the spread codes C₁ to C₁₆are supplied to the selected transmission block 125 at the same time.Then, another transmission block 125 is selected such that the spreadcodes C₁ to C₁₆ are supplied to the newly selected transmission block125 at the same time, and this process is repeated until all of thetransmission conductors 12 which form the transmission conductor array11 are supplied with the spread codes C₁ to C₁₆. However, the switchingof the transmission conductors 12 is not limited to that which usesmultiple (fixed) transmission blocks.

The modification 3 is described with reference to FIG. 29. In thepresent modification 3, the transmission conductor selection circuit 202supplies the spread codes C₁ to C₁₆ to the transmission conductors Y_(n)to Y_(n+15) which are positioned adjacent to each other from among thetransmission conductors 12 which form the transmission conductor array11. The transmission conductors Y_(n) to Y_(n+15) to be selected by thetransmission conductor selection circuit 202 are shifted (or switched)time-dependently in a direction in which the index n increases. Inparticular, the transmission conductor selection circuit 202 firstselects, for example, the transmission conductors Y₁ to Y₁₆ as seen inFIG. 29. The spread code supplying circuit 21 then supplies the spreadcodes C₁ to C₁₆ to the transmission conductors Y₁ to Y₁₆ at the sametime, respectively.

In this state, the supply of the spread codes C₁ to C₁₆ is carried outfor a predetermined period of time, and then the transmission conductorselection circuit 202 shifts (switches) the transmission conductors 12to be selected by one conductor in the direction in which the index n ofthe transmission conductors 12 increases. In particular, thetransmission conductor selection circuit 202 switches from the 16transmission conductors Y₁ to Y₁₆ selected in the previous operationcycle to the newly selected 16 transmission conductors Y₂ to Y₁₇. Then,the spread code supplying circuit 21 supplies the spread codes C₁ to C₁₆to the newly selected transmission conductors Y₂ to Y₁₇ at the sametime, respectively. Thereafter the transmission conductor selectioncircuit 202 successively repeats the switching operation described aboveto carry out supply of the spread codes C₁ to C₁₆.

It is to be noted that, while, in the modifications 2 and 3, thetransmission conductor selection circuit 202 changes (switches) thetransmission conductors 12 to be connected to the spread code supplyingcircuit 21 in a direction in which the index n of the transmissionconductors 12 increases after every predetermined interval of time, thepresent invention is not limited to this configuration. For example, thetransmission conductors 12 to be connected to the transmission conductorselection circuit 202 may be switched (shifted) in the direction inwhich the index n thereof decreases after a predetermined interval oftime. Further, the transmission conductors 12 may be selected at randomin accordance with a predetermined sequence.

5. Fifth Embodiment Selection Methods of a Reception Conductor

Although, in the first embodiment described hereinabove, the receptionconductor array 13 is divided into a plurality of detection blocks 36,and the reception conductor selection circuit 22 selects one receptionconductor 14 in each of the detection blocks 36 after everypredetermined interval of time (see FIG. 6), the present invention isnot limited to this configuration. For example, correlation calculationmay be carried out collectively for one of the detection blocks 36, andafter a predetermined interval of time, another detection block isselected for which correlation calculation is carried out collectively.

[Modification 4]

Details of a modification 4 are described with reference to FIGS. 30 and31. FIG. 30 shows a circuit configuration of the reception conductorselection circuit 131 and the amplification circuit 32 in themodification 4. Referring first to FIG. 30, in the modification 4, thereception conductor array 13 is divided into a plurality of detectionblocks 136 each including 16 reception conductors X_(m) to X_(m+15)which are positioned adjacent to each other. More particularly, thereception conductor array 13 is divided into eight detection blocks 136of the reception conductors X₁ to X₁₆, X₁₇ to X₃₂, X₃₃ to X₄₈, . . . ,X₁₁₃ to X₁₂₈.

A reception conductor selection circuit 131 includes a switch 131 awhich in turn includes 16 logic switches as seen in FIG. 30. Outputterminals 131 c of the 16 switches are connected to the I/V conversioncircuits 32 a which form the amplification circuit 32. Further, theinput terminals 131 b of the switch 131 a are connected to correspondingreception conductors 14. It is to be noted that the configuration of theother part of the reception conductor selection circuit 131 and theamplification circuit 32 is same as that of the first embodimentdescribed hereinabove with reference to FIGS. 1 and 5 and overlappingdescription of the same is omitted herein to avoid redundancy.

Operation of the reception conductor selection circuit 131 is describedwith reference to FIG. 31. The reception conductor selection circuit 131selects a predetermined detection block 136. In particular, thereception conductor selection circuit 131 first selects, for example,the detection block 136 which includes the reception conductors X₁ toX₁₆ as seen in FIG. 31. Then, the correlation value calculation circuit34 carries out correlation calculation for output signals output fromall of the reception conductors X₁ to X₁₆ which form the selecteddetection block 136, and stores a correlation value which is a result ofthe correlation calculation in the correlation value storage circuit 34d described hereinabove with reference to FIG. 8.

Then, after a predetermined interval of time, the reception conductorselection circuit 131 switches from the currently selected detectionblock 136 to another detection block 136 which includes the receptionconductors X₁₇ to X₃₂. Then, the correlation value calculation circuit34 carries out correlation calculation for the output signals outputfrom all of the reception conductors X₁₇ to X₃₂ which form the newlyselected detection block 136, and stores a resulting correlation valuein the correlation value storage circuit 34 d. Thereafter, the switchingoperation described above is repeated after every predetermined intervalof time. Then, after the correlation calculation for the output signalsfrom the detection block 136 which includes the reception conductorsX₁₁₃ to X₁₂₈ and the storage of a resulting correlation value arecompleted, the reception conductor selection circuit 131 returns to theinitially selected detection block 136 which includes the receptionconductors X₁ to X₁₆. Thereafter, similar switching and correlationcalculation are carried out.

6. Sixth Embodiment Different Examples of a Configuration of a SensorSection

In the first embodiment described hereinabove, the sensor section 100 isconfigured such that the reception conductors 14 and the transmissionconductors 12 are provided in an opposing relationship to each otherwith the spacer 16 interposed therebetween on one of the surfaces of thefirst substrate 15 as seen in FIG. 2. However, the present invention isnot limited to this configuration. For example, the reception conductors14 and the transmission conductors 12 may individually be formed on theopposite surfaces of a single glass substrate. In the following, adifferent example of a configuration of the sensor section is describedwith reference to FIG. 32.

[Modification 5]

FIG. 32 schematically shows a cross section of a sensor section 500according to the modification 5. Referring to FIG. 32, the sensorsection 500 includes a substrate 501 formed, for example, substantiallyas a flat plate and made of, for example, glass. A plurality ofreception conductors 514 are formed on one of the surfaces of thesubstrate 501, that is, on the surface of the substrate 501 to bepointed to by a pointer 19 such as a finger. A plurality of transmissionconductors 512 are formed on the other surface of the substrate 501,that is, on the lower side surface of the substrate 501 in FIG. 32.

The transmission conductors 512 are covered at the surface thereof witha first protective layer 513 formed so as to cover the overall area ofthe one surface of the substrate 501. Similarly, the receptionconductors 514 are covered with a second protective layer 515 formed soas to cover the overall area of the other surface of the substrate 501.The second protective layer 515 is further covered with a protectivesheet 516 substantially in the form of a flat plate. The protectivesheet 516 protects the reception conductors 514 so that the pointer 19may not directly touch the reception conductors 514.

It is to be noted that, in the present modification 5, the substrate501, transmission conductors 512, and reception conductors 514 can bemade of materials similar to those used in the first embodimentdescribed hereinabove. In particular, in the present modification 5, aknown glass substrate or a sheet-like or film-like substrate formed froma synthetic resin may be used for the substrate 501 similarly as in thefirst embodiment. The first protective layer 513 and the secondprotective layer 515 may be formed, for example, from a SiO₂ film or asynthetic resin film, and the protective sheet 516, for example, may beformed of a sheet material formed of a synthetic resin. Further, while,in the present modification 5, the first protective layer 513, secondprotective layer 515 and protective sheet 516 are formed so as to coverthe overall area of the opposite surfaces of the substrate 501, thepresent invention is not limited to this configuration. For example,since the intended function of the protective sheet 516 is achieved ifthe protective sheet 516 is formed such that the pointer 19 does nottouch directly with the reception conductors 514, the second protectivelayer 515 may be formed in a shape that is substantially the same asthat of the reception conductors 514.

Since the sensor section 500 according to the present modification 5makes it possible to decrease the number of substrates in comparisonwith the sensor section 100 of the first embodiment describedhereinabove with reference to FIG. 2, the thickness of the sensorsection 500 can be further reduced. Further, since the sensor section500 of the modification 5 reduces the number of required substrates, itcan be provided at a reduced cost.

[Modification 6]

Another modification to the sensor section is described with referenceto FIGS. 33A and 33B. In the present modification 6, the sensor sectionis configured such that the transmission conductors and the receptionconductors are formed, for example, on one of the opposite surfaces of asubstrate. FIG. 33A shows a cross section of the sensor section of themodification 6 and FIG. 33B shows a perspective view of the sensorsection of the modification 6. It is to be noted that, in FIGS. 33A and33B, a protective layer and a protective sheet are not shown forsimplified illustration.

Referring first to FIG. 33A, the sensor section 600 of the presentmodification 6 includes a substrate 601, a metal layer 602 formed in apredetermined pattern on one of the opposite surfaces of the substrate601 and having conductivity, an insulating layer 603 formed on the metallayer 602, and a plurality of transmission conductors 612 and aplurality of reception conductors 614. In the modification 6, the sensorsection 600 is structured such that the transmission conductors 612 andthe reception conductors 614 cross each other on one of the surfaces ofthe substrate 601, and the insulating layer 603 is interposed betweenthe transmission conductors 612 and the reception conductors 614 atlocations at which the transmission conductors 612 and the receptionconductors 614 cross each other, to electrically isolate thetransmission conductors 612 from the reception conductors 614.

Referring now to FIG. 33B, the metal layer 602 is a substantially linear(or elongated) metal member formed, for example, so as to extend in adirection perpendicular to the direction in which the receptionconductors 614 extend. The insulating layer 603 is formed so as to coverpart of the metal layer 602. A pair of transmission conductors 612 areprovided at the opposite ends of the metal layer 602 in the extendingdirection of the metal layer 602 such that they are electricallyconnected to each other by the metal layer 602. The reception conductors614 are formed on the insulating layer 603 and are electrically isolatedfrom the metal layer 602 and the transmission conductors 612. It is tobe noted that the disposition of the transmission conductors 612 and thereception conductors 614 may be reversed. Further, while, in the presentmodification 6, the transmission conductors 612, reception conductors614 and so forth are disposed on one of the opposite surfaces of thesubstrate 601 to be approached by the pointer 19 for position pointing,the transmission conductors 612, reception conductors 614 and so forthmay otherwise be disposed on the opposite surface of the substrate 601.

In the present modification 6, the substrate 601, transmissionconductors 612 and reception conductors 614 can be formed from materialssimilar to those used in the first embodiment described hereinabove. Inparticular, the substrate 601 may be formed from a known transparentglass substrate similarly as in the first embodiment or from asheet-formed or film-formed substrate made of a synthetic resin.

The metal layer 602 may be formed from a metal material having a highelectric conductivity such as, for example, Mo (molybdenum). Since thecontact area between the metal layer 602 and the transmission conductors612 is small, in order to minimize the electric resistance of the metallayer 602 and the transmission conductors 612, preferably a metalmaterial having a high electric conductivity is used for the metal layer602. The insulating layer 603 can be formed using, for example, a resistor the like.

In the sensor section 600 of the present modification 6, since thenumber of glass substrates can be reduced in comparison with the sensorsection 100 of the first embodiment described hereinabove with referenceto FIG. 2, the thickness of the sensor section 600 can be furtherreduced. Further, since the sensor section 600 of the presentmodification 6 reduces the number of substrates, the transmissionconductors 612 and the reception conductors 614 can be formedsubstantially in one layer, and therefore, the sensor section 600 can beprovided at a further reduced cost.

Where the sensor section 600 of the present modification 6 is configuredsuch that the transmission conductors 612, reception conductors 614 andso forth are disposed on the other surface of the substrate 601 oppositeto the surface to be approached by the pointer 19 for position pointing,the substrate 601 is interposed between the pointer and thesetransmission and reception conductors. Therefore, the distance betweenthe pointer and the conductors becomes greater than that in the sensorsection 500 of the modification 5, to thereby reduce the influence ofnoise from the pointer.

[Modification 7]

While, in the first to third embodiments and the modifications 1 to 6described hereinabove, the transmission conductors are formed from linerconductors extending in a predetermined direction, in the modification7, the transmission conductors have a different form.

The modification 7 is described with reference to FIGS. 34A and 34B.FIG. 34A schematically shows a configuration of the transmissionconductors and the reception conductors in the sensor section of thepresent modification 7, and FIG. 34B shows a land conductor portion ofthe transmission conductors.

Referring first to FIG. 34A, in the present modification 7, thereception conductors 714 are formed from a linear conductor of a fixedwidth. Meanwhile, the transmission conductors 712 are formed from alinear conductor portion 722 formed so as to extend in a directionperpendicular to the direction in which the reception conductors 714extend and land conductor portions 723 having a width greater than thatof the linear conductor portion 722 and being electrically connected tothe linear conductor portion 722. The reception conductors 714 and thelinear conductor portions 722 are electrically isolated from each otherat least at cross points therebetween by an insulating layer (not shown)interposed therebetween.

Referring to FIG. 34B, each land conductor portion 723 includes firstand second land portions 723 b and 723 c formed in a substantially sameshape and a substantially linear connecting portion 723 d forelectrically connecting the first and second land portions 723 b and 723c to each other. The first and second land portions 723 b and 723 c areformed in a substantially triangular shape having an apex 723 a, atwhich the land conductor portion 723 is connected to the linearconductor portion 722. The first land portion 723 b and the second landportion 723 c are electrically connected to each other at bottomportions 723 e thereof opposite to the apex 723 a by the connectingportion 723 d.

It is to be noted that, while, in FIGS. 34A and 34B, the extensiondirection of the reception conductors 714 and the extension direction ofthe transmission conductors 712 are orthogonal to each other, thepresent invention is not limited to this configuration. The extensiondirections of both conductors need not be perpendicular to each other,and it is only necessary for the extension direction of the transmissionconductors 712 and the extension direction of the reception conductors714 to cross each other so as to form cross points therebetween forposition detection purposes.

Where the land conductor portion 723 is configured in such a manner asdescribed above, a pair of recessed portions 723 f are formed on theland conductor portion 723 so as to extend along the extension directionof the reception conductors 714.

Where the transmission conductors 712 are formed in such a shape asdescribed above, the area of the transmission conductors 712 near (i.e.,in the proximity of) a cross point can be increased. As a result, when apointer approaches the sensor section 700, an increased amount ofelectric field emerging from the transmission conductors 712 convergesto the pointer, and consequently, the detection sensitivity can beimproved.

Further, if a pointer detection apparatus to which the present inventionis applied and another pointer detection apparatus which adopts theelectromagnetic resonance (EMR) system are both placed, one on theother, to form an inputting apparatus having a common pointer detectionregion for both of the two pointer detection apparatus, then eddycurrent may be generated in the land conductor portion 723 by anelectric field generated from the position detection apparatus of theelectromagnetic resistance type. This may cause the so-called eddycurrent loss, which may negatively impact the position detection by theelectromagnetic resonance system. To solve this problem, in the pointerdetection apparatus to which the present invention is applied, therecessed portions 723 f are formed on the land conductor portion 723positioned in the proximity of a cross point as in the presentmodification 7. Where another pointer detection apparatus which adoptsthe electromagnetic resonance system is additionally provided, one onthe other, generation of eddy current can be suppressed by the landconductor portion 723 having the recessed portions 723 f. Consequently,the problem as described above can be reduced.

It is to be noted that the application of the configuration of thepresent modification 7 is not limited to the sensor section of a pointerdetection apparatus of the cross point electrostatic coupling type. Theconfiguration of the modification 7 may be applied also to the sensorsection of a pointer detection apparatus of the projected capacitivetype electrostatic coupling type, which includes a conductor patternsimilar to that of the cross point electrostatic coupling type. Inparticular, the configuration of the modification 7 can be applied alsoto the sensor section of a pointer detection apparatus of the projectedcapacitive type electrostatic coupling system or the like, whichincludes a conductor pattern formed from a plurality of first conductorsdisposed in a first direction and a plurality of second conductorsdisposed in a direction crossing the first direction and wherein, basedon detection signals obtained from the conductors disposed in thesedifferent directions, those conductors which correspond to a pointedposition are specified and the position pointed to by the pointer isdetermined from the position at which the specified conductors crosseach other.

The configuration of the transmission conductors 712 and the receptionconductors 714 in the present modification 7 can be applied also to thesensor sections described hereinabove in connection with the firstembodiment in FIG. 2, the modification 5 in FIG. 32, and themodification 6 in FIGS. 33A and 33B. Further, where the pointerdetection apparatus and a display apparatus such as a liquid crystalpanel are formed as a unitary member, in order to suppress the influenceof a signal arising from pixel scanning of the liquid crystal panel, thereception conductors 714 are preferably disposed to extend in adirection that crosses the pixel scanning direction of the liquidcrystal panel.

[Modification 8]

The shape of the land conductor portion of the transmission conductorsis not limited to the example described hereinabove with reference toFIGS. 34A and 34B. FIG. 35 shows another example of a configuration ofthe shape of the land conductor portion as a modification 8. Referringto FIG. 35, a transmission conductor 812 of the sensor section 800according to the modification 8 includes a linear conductor portion 822and a land conductor portion 823 similarly as in the modification 7. Themodification 8 is different from the modification 7 in that, while theland conductor portion 723 in the modification 7 has the first andsecond land portions 723 b and 723 c of a substantially triangularshape, in the present modification 8, the land conductor portion 823 hasfirst and second land portions 823 b and 823 c having a substantiallytrapezoidal shape. In the present modification 8, the transmissionconductor 812 is electrically connected at smaller parallel sides 823 athereof, which correspond to the apexes 723 a of the first and secondland portions 723 b and 723 c in the modification 7, to the linearconductor portion 822. The remaining part of the sensor section 800 issimilar to that of the sensor section 700 described above with referenceto FIGS. 34A and 34B, and overlapping description of the commonconfiguration is omitted herein to avoid redundancy. It is to be noted,however, that corresponding elements in FIGS. 34A and 34B and 35 aredenoted by reference numbers having different first digits.Particularly, the first digit of the numbers used in the modification 7of FIGS. 34A and 34B is “7” while the first digit of the numbers used inthe modification 8 of FIG. 35 is “8.”

Comparing the present modification 8 with the modification 7, it isnoted that the land conductor portion 823 of the transmission conductor812 in the modification 8 is shaped such that it has no apex portion 723a, that is, no acute angle portion. Consequently, the flow path ofelectric current is wider through the land conductor portion 832 thanthrough the linear conductor portion 822.

As a result, concentration of current at the connecting portion betweenthe land conductor portion 823 and the linear conductor portion 822 isless likely to occur, and the current readily disperses. In particular,since current flows in a spread fashion between the smaller parallelsides 823 a, which define the opposite ends of the land conductorportion 823, the resistance value between the smaller parallel sides 823a does not increase. Since such a structure as just described isprovided, with the present modification 8, a wide flow path for currentcan be assured between the land conductor portion 823 and the linearconductor portion 822 in comparison with the modification 7. As aresult, the electric conduction characteristic can be further improvedin comparison with that of the modification 7. It is to be noted thatthe shape of the smaller parallel side 823 a preferably has no acuteangle portion and the smaller parallel side 823 a may have, for example,a curved shape different from the shape described above. Further, whilethe transmission conductor 812 of the sensor section 800 in the presentmodification 8 is configured such that the two recesses 823 f are formedin the land conductor portions 823, the number of such recesses is notlimited to two and, for example, only one or three or more recesses maybe formed.

It is to be noted that the application of the configuration of thepresent modification 8 is not limited to the sensor section of a pointerdetection apparatus of the cross point electrostatic coupling type. Theconfiguration of the modification 8 may be applied also to the sensorsection of a pointer detection apparatus of the projected capacitivetype electrostatic coupling system. Further, while, in the presentmodification 8, only the transmission conductor is formed from a linearconductor portion and a land conductor portion having a recessed portionprovided at a central portion of the conductor portion, likewise thereception conductor may have a configuration similar to that of thetransmission conductor.

Further, the configuration of the transmission conductors 812 and thereception conductors 814 in the present modification 8 can be appliedalso to the sensor sections described hereinabove in connection with thefirst embodiment in FIG. 2, the modification 5 in FIG. 32, and themodification 6 in FIG. 33. Further, where the pointer detectionapparatus and a display apparatus such as a liquid crystal panel areformed as a unitary member, in order to suppress an influence of asignal arising from pixel scanning of the liquid crystal panel, thereception conductors 814 are preferably disposed to extend in adirection that crosses the pixel scanning direction of the liquidcrystal panel.

[Modification 9]

In a pointer detection apparatus which adopts the cross pointelectrostatic coupling system, when the surface thereof on which apointer is to be operated, that is, the sensor section thereof, isviewed from above, it has a region in which a conductor patternconsisting of a plurality of reception conductors and a plurality oftransmission conductors exists and another region in which no suchconductor pattern exists. Although each conductor is formed from atransparent electrode film such as an ITO film, the transmission factorof the region in which a conductor pattern exists is lower than that ofthe region in which no conductor pattern exists. As a result,non-uniformity in transmission factor appears on the sensor section.Such non-uniformity in transmission factor sometimes irritates a user ofthe pointer detection apparatus. Therefore, a modification 9 isconfigured so as to eliminate such non-uniformity in transmission factoron the sensor section.

FIG. 36 shows a general configuration of the sensor section of themodification 9. It is to be noted that the configuration of the presentmodification 9 is applied to the sensor section 500 of the modification5 described hereinabove with reference to FIG. 32. Referring to FIG. 36,in the sensor section 510 of the modification 9, in a region in whichnone of transmission conductors 512 and reception conductors 514 exists,first transparent electrode films 517 and second transparent electrodefilms 518 made of, for example, the same material as that of theconductors are provided. The other part of the sensor section 510 hasthe same configuration as that of the sensor section 500 of themodification 5 described hereinabove with reference to FIG. 32, andoverlapping description of the same is omitted herein to avoidredundancy.

FIG. 37A shows a configuration of a transmission conductor 512 and afirst transparent electrode film 517 formed on one surface, that is, onthe lower surface, of a substrate of the sensor section 510. In thepresent modification 9, the first transparent electrode film 517 of arectangular shape is disposed on the surface of the substrate on whichthe transmission conductor 512 is provided. Each of the firsttransparent electrode film 517 is provided between two transmissionconductors 512 disposed adjacent to each other. The first transparentelectrode film 517 has a dimension a little smaller than the dimensionof the distance between the transmission conductors 512 and is spacedfrom each transmission conductor 512 with a small gap therebetween sothat it does not contact any of the transmission conductors 512. Thedimension of the first transparent electrode film 517 in the lengthwisedimension of the transmission conductors 512 is a little smaller thanthe dimension of the sum of the distance between the receptionconductors 514 disposed adjacent to each other and the conductor widthof one reception conductor 514. The first transparent electrode film 517is disposed between the two reception conductors 514 positioned adjacentto each other, such that lateral edges of the first transparentelectrode film 517 respectively extend to cover approximately ½ theconductor width of the reception conductors 514, as illustrated in FIG.37A.

FIG. 37B shows a configuration of a reception conductor 514 and a secondtransparent electrode film 518 formed on the other surface, that is, onthe upper surface, of the substrate of the sensor section 510. In thepresent modification 9, the second transparent electrode film 518 isdisposed on the surface of the substrate on which the receptionconductor 514 is disposed. Regarding the dimension of the secondtransparent electrode film 518, an approach similar to that used withthe dimension of the first transparent electrode film 517 is applied. Inparticular, the second transparent electrode film 518 has a dimension alittle smaller than the distance between the reception conductors 514 sothat it does not contact the reception conductors 514, and is spacedapart from each of the reception conductors 514 with some gap lefttherebetween. Regarding the dimension of the second transparentelectrode film 518 in the lengthwise dimension of the receptionconductor 514, it is set such that the second transparent electrode film518 partly covers the width of any adjacent transmission conductor 512.Regarding the dimension and disposition of the first transparentelectrode film 517 and the second transparent electrode film 518, theyshould be disposed such that, when the sensor section 510 is viewed, forexample, from the surface side of the sensor section 510 on which apointer is to be operated, that is, from the upper surface side, theoverlapping relationship of the transmission conductor 512, receptionconductor 514, first transparent electrode film 517, and secondtransparent electrode film 518 is made as uniform as possible while theelectric isolation from each other is maintained, so that non-uniformityof the transmission factor can be suppressed across the overall sensorsection 510 and a uniform optical characteristic can be maintained.

If the conductors and the transparent electrode films formed on thesurfaces of the glass substrate of the sensor section 510 are disposedas seen in FIGS. 37A and 37B, then when the sensor section 510 is viewedfrom above, the first transparent electrode films 517 and the secondtransparent electrode films 518 made of the same material as that of theconductors are formed in a region in which no conductor pattern existsas seen in FIG. 36. As a result, non-uniformity of the transmissionfactor on the sensor section 510 is suppressed.

It is to be noted that the shape of the first transparent electrode film517 and the second transparent electrode film 518 for suppressing thenon-uniformity of the transmission factor is not limited to arectangular shape. It is only necessary that the overlappingrelationship between the conductor pattern formed from the transmissionconductors 512 and the reception conductors 514 and the firsttransparent electrode films 517 and second transparent electrode films518, when the sensor section 510 is viewed from above, be opticallyuniform. As such, the shape of the first transparent electrode films 517and the second transparent electrode films 518 may be suitably set inrelation to the shape of the conductor pattern formed from thetransmission conductors 512 and the reception conductors 514. Forexample, while, in the present modification 9, a plurality oftransparent electrode films of a rectangular shape are disposed in aspaced-apart relationship from each other and extend along a directionin which the transmission conductors 512 or the reception conductors 514extend, the plural transparent electrode films may be alternativelyformed as a single electrode film.

The configuration of the present modification 9 can be applied also tothe sensor sections described hereinabove in connection with the firstembodiment in FIG. 2 and the modifications 6 to 8 in FIGS. 33A to 35.Furthermore, a substrate having a predetermined region in which, forexample, a transparent electrode film for prevention of thenon-uniformity in transmission factor is formed may be preparedseparately and additionally provided on the sensor section. Further, asubstrate in the form of a film may be used as described hereinabove.

[Modification 10]

While, in the first to third embodiments, both of the transmissionconductors and the reception conductors are formed linearly, the presentinvention is not limited to this configuration. For example, at leastthe transmission conductors or the reception conductors may be formed ina curved form or in a concentric relationship.

In the following, a configuration wherein a plurality of transmissionconductors are formed in circular shapes having different diameters fromeach other and disposed in a concentric relationship with each other isdescribed with reference to FIG. 38. FIG. 38 shows an arrangementpattern of a transmission conductor array 411 and a reception conductorarray 413 of a sensor section 400 according to a modification 10. In thepresent modification 10, the transmission conductor array 411 includes aplurality of transmission conductors 412 respectively having differentdiameters from each other and disposed in a concentric relationship fromeach other. The concentrically disposed transmission conductors 412 aredisposed such that the distances between adjacent ones of thetransmission conductors 412 in a radius direction are equal to eachother.

The reception conductor array 413 includes, for example, a plurality oflinear reception conductors 414 formed so as to extend radially from thecenter of the transmission conductor array 411. The reception conductors414 are disposed in an equidistantly spaced relationship from each otherin a circumferential direction of the concentric circles formed by thetransmission conductor array 411. With such configuration describedabove, the circumferential directions of the transmission conductors 412and the extension directions of the reception conductors 414 cross eachother to form a plurality of cross points.

The sensor section 400 of the modification 10 shown in FIG. 38 issuitable where the position detection region of the sensor section 400has a circular shape. It is to be noted that, while, in the modification10, the plural transmission conductors 412 which form the transmissionconductor array 411 are disposed in an equidistantly spaced relationshipfrom each other in a radial direction, the present invention is notlimited to this configuration and the distances between the transmissionconductors 412 may be suitably set to desired distances. Similarly,while, in the present modification 10 described above, the pluralreception conductors 414 which form the reception conductor array 413are disposed in an equidistantly spaced relationship from each other ina circumferential direction of the transmission conductors 412, thedistances between the reception conductors 414 may be suitably set todesired distances.

Further, while, in the modification 10 described above, the transmissionconductors 412 are formed substantially circularly and the receptionconductors 414 are formed substantially linearly, the present inventionis not limited to this configuration. For example, at least thetransmission conductors 412 or the reception conductors 414 may beformed in a meandering (serpentine) shape with respect to the extensiondirection thereof.

7. Seventh Embodiment Different Examples of a Configuration of anAmplification Circuit

While, in the first to third embodiments described hereinabove, aone-input one-output amplifier is used for the amplifier used in theamplification circuit 32 described hereinabove with reference to FIG. 1,the present invention is not limited to this configuration. For example,a differential amplifier may be used for the amplifier. Specifically, a2-input 1-output differential amplifier or a 4-input 1-outputdifferential amplifier may be used according to modifications 11 to 18,as will be described with reference to FIGS. 39 to 55. In some of thefollowing examples where a differential amplification circuit is used,the reception conductor array 13 includes 129 reception conductors 14.It is to be noted that the configuration of the other part of theamplification circuit is the same as that of the first embodimentdescribed hereinabove with reference to FIG. 1 and overlappingdescription of the same is omitted herein to avoid redundancy.

[Modification 11]

The configuration of the modification 11 is described with reference toFIG. 39. FIG. 39 shows a general configuration of the reception section310 where a 2-input 1-output differential amplifier 250 is used for theamplification circuit.

The reception conductor array 13 is divided into 16 detection blocks236. Each of the detection blocks 236 is composed of nine receptionconductors X_(m) to X_(m+8) which are positioned adjacent to each other,that is, whose indexes m are consecutive. From among the nine receptionconductors X_(m) to X_(m+8) which form each of the detection blocks 236,the reception conductor X_(m+8) which has the highest index m is usedcommonly by another detection block 236 which is positioned adjacent tothe detection block 236. In particular, in the present modification 11,the reception conductor array 13 is divided into detection blocks {X₁ toX₉}, {X₉ to X₁₇}, . . . , {X₁₁₃ to X₁₂₁} and {X₁₂₁ to X₁₂₉}.

The reception conductor selection circuit 231 includes a number of pairsof switches 231 a and 231 b equal to the number of detection blocks 236.One pair of switches 231 a and 231 b include nine input terminals 231 cwhich are common to both of the switches 231 a and 231 b. The inputterminals 231 c are connected to corresponding reception conductorsX_(m). Output terminals 231 d and 231 e of the paired switches 231 a and231 b are connected to input terminals of different I/V conversioncircuits 232 a hereinafter described. The paired switches 231 a and 231b successively switch the reception conductors 14 to be connected to theI/V conversion circuits 232 a at predetermined intervals of time. Inparticular, if it is assumed that the switch 231 a is first connected tothe reception conductor X₁ and the switch 231 b is connected to thereception conductor X₂ as seen in FIG. 39, then the switch 231 a and theswitch 231 b are switched such that the switch 231 a is connected to thereception conductor X₂ and the switch 231 b is connected to thereception conductor X₃ after the predetermined interval of time.Thereafter, the reception conductor X_(m) to be connected to the I/Vconversion circuit 232 a is successively switched at the predeterminedintervals of time. Then, after the switch 231 a is connected to thereception conductor X₈ and the switch 231 b is connected to thereception conductor X₉, the switch 231 a and the switch 231 b areswitched such that the switch 231 a is again connected to the receptionconductor X₁ and the switch 231 b is again connected to the receptionconductor X₂.

The reception section 310 includes the reception conductor selectioncircuit 231, an amplification circuit 232, an A/D conversion circuit 33,a correlation value calculation circuit 34 and a position detectioncircuit 35, as seen in FIG. 39.

The amplification circuit 232 includes a plurality of I/V conversioncircuits 232 a, a plurality of differential amplifiers 250, and achangeover switch 232 d. The number of I/V conversion circuits 232 a isequal to the total number of the switches 231 a and 231 b, that is, 32(2×16), and the input terminals 231 c of the paired switches 231 a and231 b are connected to corresponding reception conductors 14, while theoutput terminals 231 d and 231 e of the paired switches 231 a and 231 bare respectively connected to the corresponding I/V conversion circuits232 a. The I/V conversion circuit 232 a connected to the switch 231 afrom between the paired switches 231 a and 231 b is connected to thenegated input terminal, which has the negative polarity (−), of thecorresponding differential amplifier 250 while the output terminal ofthe other I/V conversion circuit 232 a connected to the switch 231 b isconnected to the non-negated input terminal, which has the positivepolarity (+), of the differential amplifier 250.

Each differential amplifier 250 is a 2-input 1-output differentialamplifier. The differential amplifier 250 differentially amplifiesoutput signals from the I/V conversion circuits 232 a connected to thetwo input terminals thereof and outputs a resulting amplified signal.The output signal output from the differential amplifier 250 isamplified to a signal level by an amplifier not shown and then receivedby the A/D conversion circuit 33 through the changeover switch 232 d.

Since the modification 11 is configured in such a manner as describedabove, noise superposed in output signals from the reception conductors14 is removed by the differential amplification by the differentialamplifiers 250 of the amplification circuit 232. Consequently, the noiseresisting property of the pointer detection apparatus can be improved.

[Modification 12]

While, in the modification 11 described above, a single receptionconductor 14 is connected to each input terminal of the differentialamplifiers 250 through an I/V conversion circuit 232 a, the number ofreception conductors 14 to be connected to each of the input terminalsof a differential amplifier may be a plural number. An example of theform just described is shown in FIG. 40.

FIG. 40 shows a general configuration of the amplification circuit ofthe present modification 12. While the reception conductor selectioncircuit 231 in the modification 11 is formed from a plurality of pairsof switches 231 a and 231 b for selecting two reception conductors 14 asseen in FIG. 39, in the present modification 12, though not particularlyshown in FIG. 40, five switches are provided in place of the pairedswitches 231 a and 231 b such that five reception conductors X_(m−2) toX_(m+2) which are positioned adjacent to each other are connected toinput terminals of a differential amplifier 350 through the fiveswitches.

The reception conductor selection circuit 231 shown in FIG. 39 connects,for example, four reception conductors X_(m−2), X_(m−1) and X_(m+1),X_(m+2) of five arbitrary reception conductors X_(m−2) to X_(m+2) whichare positioned on the opposite sides to the input terminals of thedifferential amplifier 350. It is to be noted that, also in the presentmodification 12, output signals of the reception conductors X_(m−2) toX_(m+2) selected by the reception conductor selection circuit 231 arefirst converted into voltage signals by the I/V conversion circuit 232 aand supplied to the input terminals of the differential amplifier 350.However, since the configuration of the modification 12 in this regardis the same as that of the modification 11 described hereinabove withreference to FIG. 39, for ease of illustration, the reception conductorselection circuit 231 and the I/V conversion circuit 232 a are omittedin FIG. 40.

In the illustrated example, of the five reception conductors X_(m−2) toX_(m+2) selected by the reception conductor selection circuit 231, thereception conductors X_(m−2) and X_(m−1) are connected to the negatedinput terminals of the differential amplifier 350 which have thenegative or (−) polarity, and the reception conductors X_(m+2) andX_(m+1) are connected to the non-negated input terminals of thedifferential amplifier 350 which have the positive or (+) polarity. Thecentrally positioned reception conductor X_(m) is connected to theground. It is to be noted that the centrally positioned receptionconductor X_(m) may be connected to the ground or to an input terminalof the differential amplifier 350 which is set to a predeterminedreference voltage level such as, for example, a reference level or asupply voltage level Vcc inside the differential amplifier 350.

Where such a configuration as just described is adopted, output signalsfrom the plural reception conductors X_(m−2) to X_(m+2) are input at thesame time to the differential amplifier 350. As a result, since thelevel of the differential signal output from the differential amplifier350 increases, the detection sensitivity can be improved. Further, sincethe number of reception conductors 14 connected to the differentialamplifier 350 increases, the detection range for a pointer can also beexpanded. Further, in the present modification 12, since thedifferential amplifier 350 is used in the amplification circuit 232shown in FIG. 39, the noise resisting property can be improved similarlyas in the modification 11.

The reason why the centrally positioned reception conductor X_(m) is setto the ground or the predetermined reference voltage level in thepresent modification 12 is as follows. As described hereinabove inconnection with the first embodiment, in the pointer detection apparatusof the cross point electrostatic coupling system, the variation of thecurrent at a cross point at which current is shunted to the groundthrough the pointer 19 is detected (see FIG. 12B). However, if thepointer 19 is not grounded sufficiently, then the shunting of current atthe cross point becomes insufficient. In this instance, the currentvariation at the cross point becomes small, and the sensitivity inposition detection deteriorates.

In contrast, if the voltage level of the reception conductor X_(m) whichis positioned at the center from among the plurality of receptionconductors X_(m−2) to X_(m+2) connected to the differential amplifier350 is set to the ground or a reference voltage level such as, forexample, a power supply voltage level or the ground voltage level as inthe present modification 12, then even if the pointer 19 is not groundedsufficiently, as long as the pointer 19 touches the reception conductorX_(m), part of the current can be surely shunted through the pointer 19and the reception conductor X_(m). As a result, deterioration of thesensitivity described above can be suppressed.

In the modifications 11 and 12, a differential amplifier is used in theamplification circuit to improve the detection sensitivity. Thedetection sensitivity can be further improved by supplying the samespread code to a plurality of transmission conductors, as will bedescribed below.

[Modification 13]

A modification 13 is described with reference to FIG. 41. In the presentmodification 13, the same spread code is supplied to two transmissionconductors which are positioned adjacent to each other as seen in FIG.41. It is to be noted that the configuration of the other part is thesame as that of the modification 11 described hereinabove with referenceto FIGS. 1, 39 and so forth, and therefore, overlapping description ofthe same is omitted herein to avoid redundancy.

As seen in FIG. 41, each of 16 different spread codes C₁ to C₁₆ producedby a plurality of spread code production circuits 24 which form thespread code supplying circuit 21 is supplied to two transmissionconductors 12 positioned adjacent to each other. In particular, thespread code C₁ is supplied to the transmission conductors Y₁ and Y₂, thespread code C₂ to the transmission conductors Y₅ and Y₆, . . . , thespread code C₁₅ to the transmission conductors Y₅₇ and Y₅₈, and thespread code C₁₆ to the transmission conductors Y₆₁ and Y₆₂. Though notparticularly shown, the transmission conductor selection circuit 22(FIG. 1) time-dependently switches the transmission conductors 12 to beconnected to the spread code production circuits 24 such that the spreadcodes C₁ to C₁₆ are supplied, eventually, to all transmission conductors12 which form the transmission conductor array 11.

For example, referring to an arbitrary one of the reception conductors14 (not shown), if the same spread code is supplied to two transmissionconductors, then since twice the spread code is supplied to thereception conductor 14 as compared to the reception conductor 14 in thefirst embodiment, the output signal from the arbitrary receptionconductor 14 is also doubled. Accordingly, the detection sensitivity canbe improved. Further, if the same spread code is supplied at the sametime to three or more transmission conductors 12, then the detectionsensitivity in regard to an arbitrary one of the reception conductors 14can be further improved by an amount corresponding to the number oftransmission conductors to which the same spread code is supplied at thesame time.

[Modification 14]

Where the same spread code is supplied to a plurality of transmissionconductors 12 positioned adjacent to each other as in the case of themodification 13 described hereinabove with reference to FIG. 41,preferably output signals of a number of reception conductors 14 equalto the number of transmission conductors 12 to which the same spreadcode is supplied are amplified.

A general configuration of the modification 14 is described withreference to FIG. 42. FIG. 42 shows a general configuration of anamplification circuit where the same spread code C_(k) is supplied totwo transmission conductors Y_(n) and Y_(n+1) positioned adjacent toeach other. It is to be noted that the configuration of the other partthan that shown in FIG. 42 is the same as that of the modification 11,and illustration in the drawings and description in the specification ofthe same are omitted for ease of illustration and description.

Where the same spread code C_(k) is supplied to the two transmissionconductors Y_(n) and Y_(n+1) positioned adjacent to each other as in thecase of the modification 13 described hereinabove, an amplifier whichhas a number of input terminals equal to the number of transmissionconductors 12 to which the same spread code C_(k) is supplied is used.Also, in the illustrated example, the input terminals have the samepolarity and, for example, a 2-input 1-output amplifier 360 having twonon-negated (“+”) terminals is used as the amplification circuit 232 ofthe reception section 310. To the two input terminals of the amplifier360 of the reception section 310, two reception conductors X_(m) andX_(m+1) which are positioned adjacent to each other are connected.

Where the same spread code C_(k) is supplied to the two transmissionconductors Y_(n) and Y_(n+1) positioned adjacent to each other and theoutput signals from two reception conductors X_(m) and X_(m+1)positioned adjacent to each other are amplified as described above, notonly the signal level of the output signal from the amplifier 360 isincreased, but also the detection range for a pointer can be expanded.As a result, since the time required for detection of the entire sensorsection 100 described hereinabove with reference to FIG. 1 can bereduced, the present modification 14 is suitably applied to a sensorsection which has a large position detection region. It is to be notedthat, while, in the modification 14, the number of reception conductors14 to be connected at the same time to the amplifier 360 is two, thepresent invention is not limited to this configuration. For example,three or more reception conductors 14 may be connected. In thisinstance, it is possible to further reduce the time required fordetection of the entire sensor section 100 and increase the signal levelof the output signal to be output from the amplification circuit.

If the number of transmission conductors 12 to which the same spreadcode C_(k) is supplied is set equal to the number of receptionconductors 14 to be selected at the same time as described above, thefollowing advantages are achieved. In the following, such advantages aredescribed with reference to FIGS. 42 and 43 for comparison. FIG. 43illustrates a concept of a minimum detection area S_(min)′ where thesame spread code C_(k) is supplied to two transmission conductors Y_(n)and Y_(n+1) and an output signal from an arbitrary one receptionconductor X_(m) is amplified.

Where the number of transmission conductors 12 to which the same spreadcode C_(k) is to be supplied and the number of reception conductors 14to be selected at the same time by the reception conductor selectioncircuit, that is, the number of reception conductors 14 to be connectedto an amplifier 361, are different from each other, the minimumdetection area S_(min)′ on the sensor section has a rectangular shape asseen in FIG. 43, and anisotropy occurs with the sensitivitydistribution. In this instance, for example, if a pointer has acircular-shape surface that opposes the sensor section (such surface ishereinafter referred to as an opposing surface), then the opposingsurface of the pointer is sometimes detected not as a circular shape butas a distorted shape such as an elliptic shape. In contrast, where thenumber of transmission conductors 12 to which the same spread code C_(k)is to be supplied and the number of reception conductors 14 to beconnected to the amplifier 361 are equal to each other as in themodification 14, the minimum detection area S_(min) on the sensorsection has a square shape as seen in FIG. 42 and an isotropicsensitivity distribution is achieved. In this instance, even if apointer having a circular opposing surface is placed on the sensorsection, the opposing surface of the pointer can be detected as acircular shape.

It is to be noted that, while, in the present modification 14, both ofthe number of transmission conductors 12 to which the same spread codeC_(k) is supplied and the number of reception conductors 14 to beconnected to the amplifier 360 are two, the present invention is notlimited to this configuration. Both of the number of transmissionconductors 12 to which the same spread code C_(k) is supplied and thenumber of reception conductors 14 to be connected to the amplifier 361may alternatively be three or more.

Switching of two transmission conductors, to which the same spread codeis to be supplied in the modification 14 described above, is describedwith reference to FIGS. 44A to 45C. It is to be noted that the followingdescription is given suitably with reference to FIG. 1.

FIGS. 44A and 44B illustrate an example of switching of two transmissionconductors to which the spread code C_(k) is supplied at the same time.It is assumed that, in the switching example illustrated in FIGS. 44Aand 44B, the spread code C_(k) is supplied to the transmissionconductors Y_(n) and Y_(n+1) at a certain point of time as seen in FIG.44A. Then, after lapse of a predetermined interval of time, the spreadcode C_(k) is supplied to the transmission conductors Y_(n+2) andY_(n+3) as seen in FIG. 44B. Thereafter, though not shown, thetransmission conductors 12 to which the spread code C_(k) is suppliedare switched to the transmission conductors Y_(n+4) and Y_(n+5), thetransmission conductors Y_(n+6) and Y_(n+7), and so forth. After thespread code C_(k) is supplied to the last pair of predeterminedconductors, the two transmission conductors to which the spread codeC_(k) is to be supplied at the same time are switched back to the firsttransmission conductors Y_(n) and Y_(n+1). Thereafter, the switchingsequence described above is repeated.

Another example wherein the transmission conductors 12 are successivelyswitched (shifted) by one transmission conductor is described withreference to FIGS. 45A to 45C. In particular, the spread code C_(k) issupplied to the transmission conductors Y_(n) and Y_(n+1) first at acertain point of time as seen in FIG. 45A. Then, after lapse of apredetermined interval of time, the spread code C_(k) is supplied to thetransmission conductors Y_(n+1) and Y_(n+2) as seen in FIG. 45B.Further, after another lapse of a predetermined interval of time, thespread code C_(k) is supplied to the transmission conductors Y_(n+2) andY_(n+3) as seen in FIG. 45C. Thereafter, though not particularly shown,the transmission conductors 12 to which the spread code C_(k) is to besupplied are successively switched to the transmission conductorsY_(n+3) and Y_(n+4), the transmission conductors Y_(n+4) and Y_(n+5),and so forth. Then, after the spread code C_(k) is supplied to the lastpair of predetermined conductors, the transmission conductors 12 towhich the spread code C_(k) is to be supplied are switched back to thefirst transmission conductors Y_(n) and Y_(n+1), whereafter theswitching sequence described above is repeated. In particular, in theswitching example illustrated in FIGS. 45A to 45C, the transmissionconductors 12 to which the same spread code C_(k) is supplied areselected in a unit of a predetermined number (two in the exampledescribed) after every predetermined interval of time. Then, theswitching operation is controlled such that some of the pluraltransmission conductors 12 selected by a preceding selection operation(one in the example described) is or are again selected as part of aplurality of transmission conductors 12 in the next selection operation.

[Modification 15]

While, in the modifications 13 and 14 described above, the same spreadcode is supplied to two transmission conductors positioned adjacent toeach other and output signals of two reception conductors positionedadjacent to each other are amplified by a simple amplifier, the presentinvention is not limited to this configuration. For example, thetransmission section may supply the same spread code to a plurality oftransmission conductors disposed at a predetermined number of intervals,and similarly the reception section may be configured such that outputsignals output from a plurality of reception conductors disposed at apredetermined number of intervals are amplified by an amplifier. Anexample thereof will be shown in FIG. 46 as modification 15.

In the present modification 15, in place of each of the differentialamplifiers 250 provided in the amplification circuit 232 describedhereinabove with reference to FIG. 39, an amplifier 361 having a numberof input terminals of the same polarity equal to the number oftransmission conductors 12 to which the same spread code C_(k) issupplied, for example, a 2-input 1-output amplifier 361 having, forexample, two non-negated (“+”) terminals, may be used in theamplification circuit 232 of the reception section 310. It is to benoted that, since the configuration of the part other than thatdescribed above is the same as that of the modification 14, descriptionof the same is described suitably with reference to FIGS. 1 and 39 andoverlapping description of the same is omitted.

FIG. 46 schematically shows a configuration where a transmissionconductor connected to the ground is positioned between two transmissionconductors to which the same spread code C_(k) is supplied and thereception section amplifies output signals from two reception conductorsby means of an amplifier while a reception conductor connected to theground is positioned between the two reception conductors. Inparticular, as seen in FIG. 46, the transmission conductor selectioncircuit 22 (shown in FIG. 1) selects two arbitrary transmissionconductors Y_(n+1) and Y_(n+3). Then, the spread code supplying circuit21 of the transmission section 200 supplies the same spread code C_(k)to the two selected transmission conductors Y_(n+1) and Y_(n+3).Simultaneously, the transmission conductor selection circuit 22 connectsthe transmission conductors 12 other than the two transmissionconductors Y_(n+1) and Y_(n+3) to which the spread code C_(k) is to besupplied, that is, the transmission conductors Y_(n) and Y_(n+2) and anyother remaining transmission conductors 12, to the ground.

Simultaneously, the reception conductor selection circuit 231 of thereception section 310 shown in FIG. 39 connects the two receptionconductors X_(m) and X_(m+2) to input terminals of one amplifier 361,and the amplifier 361 amplifies the output signals from the receptionconductors X_(m) and X_(m+2) connected thereto. Simultaneously, thereception conductors 14 other than the reception conductors X_(m) andX_(m+2) connected to the amplifier 361, in particular, the receptionconductors X_(m+1) and X_(m+3) and any other remaining receptionconductors 14, are connected to the ground. It is to be noted thatswitching of the transmission conductors 12 and the reception conductors14 by the transmission conductor selection circuit 22 and the receptionconductor selection circuit 231, respectively, is carried out similarlyto the switching described hereinabove, for example, in connection withthe modification 14 with reference to FIGS. 44A to 45C.

In this manner, since, in the modification 15, the same spread code issupplied to a plurality of transmission conductors 12 and output signalsfrom the plurality of reception conductors 14 are added by an amplifier361 similarly as in the modification 13, the detection range can beexpanded and the signal level to be detected can be increased, while thedetection sensitivity is also improved. The present modification 15 isparticularly suitable where the position detection range on the sensorsection is large because the minimum detection area S_(min) can beexpanded.

In the present modification 15, where the number of transmissionconductors to which the same spread code is to be supplied and thenumber of reception conductors to be selected simultaneously are setequal to each other similarly as in the modification 13 describedhereinabove, the minimum detection area S_(min) on the sensor sectioncan be set to a square shape. As a result, in the minimum detection areaon the sensor section, an isotropic sensitivity distribution can beachieved similarly as in the modification 13. In this instance, even if,for example, a pointer having a circular opposing surface is disposed onthe sensor section, the opposing surface of the pointer can be detectedas a circular shape.

[Modification 16]

The current carrying the spread codes C_(k) to be supplied to thetransmission conductor array 11 is much greater than the variationamount of an output signal caused by current flowing to the groundthrough a pointer 19 when the pointer 19 is placed at a cross point.Although raising the signal level of the output signal as in themodifications 11 to 15 improves the detection sensitivity, raising theoutput signal level may decrease the accuracy in detecting the variationamount of the output signal. In order to maintain the detectionaccuracy, it may be necessary to enhance the resolution of the A/Dconversion circuit 33 of the reception section 300 (see FIG. 1).

However, if the resolution of the A/D conversion circuit 33 is enhanced,then this may cause another problem that the scale of the A/D conversioncircuit 33 increases and designing such A/D conversion circuit 33 may bedifficult. This problem may be exacerbated where the same spread code issupplied to a plurality of transmission conductors 12.

Thus, a modification 16 which solves this problem is described withreference to FIGS. 47A to 49. FIG. 47A shows a general configuration ofthe modification 16 and FIG. 47B illustrates a waveform of an outputsignal of a differential amplifier in the modification 16. Further, FIG.48 illustrates an example of an internal configuration of a transmissionconductor selection circuit in the modification 16, and FIG. 49illustrates a configuration of a reception conductor selection circuitin the modification 16. It is to be noted that the modification 16 isdescribed in connection with a variation of an output signal where apointer 19 is placed at a cross point between the transmission conductorY_(n+2) and the reception conductor X_(m+1) as indicated by a solid linein FIG. 47A.

First, a general configuration of the modification 16 is described withreference to FIG. 47A. The modification 16 is different from themodification 11 in that two inverters 381 are provided between thespread code supplying circuit 21 for supplying the spread code C_(k) andthe transmission conductor selection circuit 382 for selectivelysupplying the spread code C_(k) to the transmission conductor array 11,and that a 4-input 1-output differential amplifier 380 is used as theamplification circuit to differentially amplifies outputs from fourreception conductors 14. Since the configuration of the other part ofthe modification 16 is the same as that of the modification 11 describedhereinabove with reference to FIGS. 1 and 39, overlapping description ofthe same is omitted herein to avoid redundancy.

The two inverters 381 invert the spread code C_(k) supplied thereto fromthe spread code supplying circuit 21 and output the inverted spreadcode. The spread code C_(k) supplied from the spread code supplyingcircuit 21 and the reversed code C_(k) output from the inverters 381 aresupplied to four transmission conductors Y_(n) to Y_(n+3) positionedadjacent to each other by the transmission conductor selection circuit382. In particular, the spread code C_(k) supplied from the spread codesupplying circuit 21 is supplied to the two transmission conductorsY_(n+2) and Y_(n+3) through the transmission conductor selection circuit382. Further, the spread code C_(k) is inverted into the reversed codesC_(k) by the inverters 381 and then supplied to the transmissionconductors Y_(n) and Y_(n+1) through the transmission conductorselection circuit 382. It is to be noted that, in the followingdescription of the supplying form (hereinafter referred to as a supplypattern) of the spread codes illustrated in FIG. 47A, each transmissionconductor to which the spread code C_(k) is supplied is represented by“+” and each transmission conductor to which the reversed code C_(k) issupplied is represented by “−.” In particular, such signal supplypattern as illustrated in FIG. 47A is represented as “−−++.”

Next, details of the transmission conductor selection circuit 382 aredescribed with reference to FIG. 48.

The transmission conductor array 11 is divided into 16 transmissionblocks 383 each including seven transmission conductors Y_(n) to Y_(n+6)positioned adjacent to each other. The transmission conductor selectioncircuit 382 is, for example, a known logic circuit and includes a numberof switch groups 382 a equal to the number of transmission blocks 383,that is, 16 switch groups 382 a. Each of the transmission blocks 383uses those three transmission conductors 12 which have the highestindexes n from among the seven transmission conductors Y_(n) to Y_(n+6)commonly with an adjacent transmission block. In particular, as seen inFIG. 48, the first transmission block 383 uses the three transmissionconductors Y_(n+4) to Y_(n+6) having the highest indexes n from amongthe transmission conductors Y_(n) to Y_(n+6) commonly with an adjacent,second transmission block 383.

Each of the switch groups 382 a includes four switches 382 a ₁, 382 a ₂,382 a ₃ and 382 a ₄. Seven terminals 382 b on the output side of each ofthe switch groups 382 a are connected to corresponding transmissionconductors Y_(n) to Y_(n+6), respectively. Input terminals 382 c of theswitches 382 a ₁ and 382 a ₂ from among the four switches 382 a ₁, 382 a₂, 382 a ₃ and 382 a ₄ are connected to the spread code productioncircuits 24 of the spread code supplying circuit 21 shown in FIGS. 1 and3 through inverters 381. The input terminals 382 c of the switches 382 a₃ and 382 a ₄ are connected to the spread code production circuits 24 ofthe spread code supplying circuit 21.

As seen in FIG. 48, for example, the switch group 382 a, to which thespread code C_(k) and the reversed code C_(k) of the spread code C_(k)are supplied, supplies the spread code C_(k) to the transmissionconductors Y_(n+2) and Y_(n+3) and supplies the reversed code C_(k) tothe transmission conductors Y_(n) and Y_(n+1). Then, after the spreadcode C_(k) and the reversed code C_(k) are supplied for a predeterminedperiod of time, the switch group 382 a switches the transmissionconductors 12 to be connected to the spread code supplying circuit 21such that the spread code C_(k) is supplied to the transmissionconductors Y_(n+3) and Y_(n+4) and the reversed code C_(k) is suppliedto the transmission conductors Y_(n+1) and Y_(n+2). Thereafter, theswitch 382 a successively and time-dependently switches the transmissionconductors to be connected to the spread code supplying circuit 21.Then, after the spread code C_(k) is supplied to the transmissionconductors Y_(n+5) and Y_(n+6) and the reversed code C_(k) is suppliedto the transmission conductors Y_(n+3) and Y_(n+4), the spread codeC_(k) is again supplied to the transmission conductors Y_(n+2) andY_(n+3) and the reversed code C_(k) is again supplied to thetransmission conductors Y_(n) and Y_(n+1), and thereafter the sequenceof operations described above is repeated. The spread code C_(k) and thereversed code C_(k) of the spread code C_(k) supplied from the spreadcode supplying circuit 21 are supplied to all of the transmissionconductors 12 which form the transmission conductor array 11 in themanner described above.

Next, details of a reception conductor selection circuit 384 in themodification 16 are described with reference to FIGS. 47A and 49.

As seen in FIG. 49, the reception conductor selection circuit 384includes a switch group 384 a which includes four switches. Inputterminals 384 b of the switch group 384 a are respectively connected tocorresponding reception conductors 14. Output terminals 384 c of theswitches of the switch group 384 a are connected to input terminals ofan I/V conversion circuit 385 a of an amplification circuit 385. Theswitch group 384 a switches the reception conductors 14 to be connectedto the I/V conversion circuit 385 a at predetermined intervals of time.Output signals from the reception conductors 14 are converted intovoltage signals by the I/V conversion circuit 385 a and input to adifferential amplifier 386 hereinafter described. It is to be notedthat, in FIG. 49, a plurality of I/V conversion circuits 385 a and aplurality of switch groups 384 a are omitted for simplicity ofillustration.

The amplification circuit 385 includes four I/V conversion circuits 385a and a differential amplifier 386. As seen in FIG. 49, the I/Vconversion circuits 385 a are connected at an input terminal thereof tooutput terminals 384 c of the switches which form the switch group 384 aand are connected at output terminals thereof to input terminals of thedifferential amplifier 386 hereinafter described.

The differential amplifier 386 is a 4-input 1-output differentialamplifier. The differential amplifier 386 is provided between the I/Vconversion circuits 385 a and the A/D conversion circuit 33 (shown inFIG. 1), and of the four input terminals thereof, the two inputterminals on the left side in FIG. 49 have the polarity of “+” while thetwo input terminals on the right side in FIG. 49 have the polarity of“−.” In particular, the polarity of the input terminals of thedifferential amplifier 386, to which the two reception conductors X_(m)and X_(m+1) having relatively low indexes m from among the fourreception conductors X_(m) to X_(m+3) which are selected by thereception conductor selection circuit 384 are connected, is set to “+.”The polarity of the other two input terminals of the differentialamplifier 386, to which the two reception conductors X_(m+2) and X_(m+3)having relatively high indexes m are connected, is set to “−.” Thedifferential amplifier 386 differentially amplifies output signalsconverted into voltage signals by the I/V conversion circuits 385 a andoutputs the resulting amplified signal.

The reception conductor selection circuit 384 carries out selectionswitching similar to that in the modification 4 described hereinabovewith reference to FIG. 31. In particular, the switch group 384 a of thereception conductor selection circuit 384 connects the receptionconductors X_(m) to X_(m+3) to the “+” terminals and the “−” terminalsof the differential amplifier 386 as seen in FIG. 49 in the orderbeginning with the reception conductor having the lowest index (e.g., X₁to X₄). In particular, the two “+” terminals of the differentialamplifier 386 are connected to the reception conductors X₁ and X₂ andthe two “−” terminals of the differential amplifier 386 are connected tothe reception conductors X₃ and X₄. Then, after a predetermined intervalof time elapses, the switch group 384 a of the reception conductorselection circuit 384 connects reception conductors positioned in thedirection in which the index m increases, that is, the receptionconductors X₂ and X₃, to the “+” terminals of the differential amplifier386, and connects the reception conductors X₄ and X₅ to the “−”terminals of the differential amplifier 386. After the switching, newoutput signals are obtained from the reception conductors X₂ to X₅ nowconnected to the switch group 384 a. Thereafter, the switch group 384 aof the reception conductor selection circuit 384 successively switchesthe reception conductors 14 to be connected to the differentialamplifier 386 at predetermined intervals of time. Then, after the lastfour reception conductors X₁₂₈ to X₁₃₁ are connected to the differentialamplifier 386, the initial state, that is, the state illustrated in FIG.49, is restored, and then the sequence of operations described above isrepeated.

Then, every time such switching as described above is carried out, thedifferential amplifier 386 differentially amplifies the output signalsinput thereto from the reception conductors 14 and outputs the resultingsignal to the A/D conversion circuit 33 at the succeeding stage shown inFIG. 1. Thereafter, the output signals digitally converted by the A/Dconversion circuit 33 are subjected to correlation calculation by thecorrelation value calculation circuit 34, and a correlation value whichis a result of the correlation calculation is stored in the correlationvalue storage circuit 34 d as seen in FIG. 8. It is to be noted that, inthe following description of the reception form (hereinafter referred toas a detection pattern) of the differential amplifier 386 illustrated inFIG. 49, each reception conductor connected to a “+” terminal of adifferential amplification circuit is represented by “+” and eachreception conductor connected to a “−” terminal of a differentialamplification circuit is represented by “−.” In particular, such signaldetection pattern as illustrated in FIG. 49 is represented as “++−−.”

Next, displacement of output signals when the reception conductors to beconnected to the four input terminals of the differential amplifier 386are switched as described above is described with reference to FIG. 47B.A curve 380 indicated by a broken line in FIG. 47B represents a waveformof an output signal output from the differential amplifier 386 when thereception conductors to be connected to the four input terminals of thedifferential amplifier 386 are successively switched beginning with thereception conductors having the lowest indexes m, and a curve 380Xindicates a waveform after the output signal from the differentialamplifier 386 is integrated. It is to be noted that, for the convenienceof description, the four input terminals of the differential amplifier386 are referred to as input terminals 386 a to 386 d in the orderbeginning with the input terminal connected to the reception conductorhaving the highest index m.

If the reception conductor selection circuit 384 successively switchesthe reception conductors 14 to be connected to the input terminals 386 ato 386 d of the differential amplifier 386 in such a manner as describedabove, then when the reception conductors 14 connected to the inputterminals 386 a to 386 d of the differential amplifier 386 arepositioned so as not to be influenced by the pointer 19 (i.e., thepointer 19 is not adjacent to any of the four reception conductors 14),then the output signal from the differential amplifier 386 is zero (see380 a of FIG. 47B).

Then, when the reception conductors 14 are approached by the pointer 19,the first to approach the pointer 19 is the right-most receptionconductor 14 connected to the input terminal 386 a of the differentialamplifier 386. Thus, the signal input to the “−” terminal of thedifferential amplifier 386 gradually decreases. As a result, the outputsignal from the differential amplifier 386 is deflected to the positiveside (see 380 b of FIG. 47B). Thereafter, when the reception conductorselection circuit 384 switches the reception conductors 14 to beconnected to the differential amplifier 386 (to the right), both of thereception conductors 14 connected to the input terminals 386 a and 386 bof the differential amplifier 386 now approach the pointer 19.Consequently, the output signal from the differential amplifier 386 isfurther deflected to the positive side. The signal level of the outputsignal from the differential amplifier 386 becomes highest when theposition at which the pointer 19 is placed is between the receptionconductors 14 connected to the input terminals 386 a and 386 b of thedifferential amplifier 386 (see 380 c of FIG. 47B).

As the reception conductor selection circuit 384 successively switchesthe reception conductors 14 to be connected to the input terminals 386 ato 386 d of the differential amplifier 386, the reception conductors 14previously connected to the input terminals 386 a and 386 b of thedifferential amplifier 386 are gradually moved away from the pointer 19,and the reception conductor 14 connected to the input terminal 386 c ofthe differential amplifier 386 now closely approaches the pointer 19instead. Consequently, the signal input to the “+” terminals of thedifferential amplifier 386 gradually decreases while the signal input tothe “−” terminals of the differential amplifier 386 gradually increases.As a result, the output signal from the differential amplifier 386 isdeflected to the negative side (see 380 d of FIG. 47B).

Then, when the pointer 19 is positioned between the reception conductor14 connected to the input terminal 386 c and the reception conductor 14connected to the input terminal 386 d, the signal input to the “+”terminal of the differential amplifier 386 becomes the lowest. As aresult, the output signal from the differential amplifier 386 decreasesmost (see 380 e of FIG. 47B).

Then, if the reception conductor selection circuit 384 further switchesthe reception conductors 14 connected to the input terminals 386 a to386 d of the differential amplifier 386, then since all of the receptionconductors 14 connected to the input terminals 386 a to 386 d of thedifferential amplifier 386 will be moved away from the pointer 19, thesignals input to the “+” terminals of the differential amplifier 386gradually increase. Consequently, the output signal from thedifferential amplifier 386 gradually increases also (see 380 f of FIG.47B). Thereafter, when the reception conductors 14 connected to theinput terminals 386 a to 386 d of the differential amplifier 386 areswitched to those reception conductors 14 which are so positioned as tobe not influenced by the pointer 19, then the output signal from thedifferential amplifier 386 becomes zero again (see 380 g of FIG. 47B).

The output signal from the differential amplifier 386 thus exhibits sucha level variation as indicated by the curve 380 of a broken line in FIG.47B. If the output signal from the differential amplifier 386 isintegrated, then the curve 380X indicated by a solid line in FIG. 47B isobtained. Then, the center of gravity of a convexed portion of the curve380X is calculated to determine (detect) the position of the pointer 19.

The output signal from the differential amplifier 386 and the valueobtained by integration of the output signal illustrated in FIG. 47Brepresent an output characteristic where the pointer 19 is placed at thecross point between the transmission conductor 12 to which the spreadcode C_(k) is supplied and the reception conductor 14. Where the pointer19 is placed at the cross point between the transmission conductor 12 towhich the reversed code C_(k) is supplied and the reception conductor 14(for example, at the cross point between the transmission conductorY_(n) and the reception conductor X_(m+1) at which the pointer 19indicated by a broken line in FIG. 47A is placed), the output signalfrom the differential amplifier 386 exhibits a characteristic oppositeto the output characteristic described above.

Where the configuration example described above in connection with thepresent modification 16 is used, the detection accuracy can bemaintained without increasing the circuit scale, and the differentialsignal to be output from the differential amplifier 386 can beincreased. Furthermore, the range within which simultaneous detectioncan be carried out can be expanded. Consequently, the detectionsensitivity can be improved. Still further, since the presentmodification 16 is configured such that the spread codes C_(k) and thereversed codes C_(k) of the spread codes C_(k) are supplied to thetransmission conductors 12, in a situation in which the pointer 19 doesnot exist, the spread codes C_(k) and the reversed code C_(k) canceleach other. Consequently, the dynamic range of the output signal of thedifferential amplifier 386 and the input signal to the A/D conversioncircuit can be suppressed. Additionally, since noise is canceled out,the noise withstanding property can be improved.

In the present modification 16, the total number of the transmissionconductors 12 to which the same spread code C_(k) is supplied and thetransmission conductors 12 to which the reversed code C_(k) having thesign reversed from the spread code C_(k) is supplied, is made equal tothe number of reception conductors 14 to be connected to thedifferential amplifier 386 similarly as in the modification 14. As aresult, in the configuration of the present modification 16 also, theminimum detection area S_(min) on the sensor section becomes a squareshape. Consequently, in the minimum detection area S_(min) on the sensorsection, an isotropic sensitivity distribution can be achieved similarlyas in the modification 14. In this instance, for example, even if apointer having a circular opposing surface is disposed on the sensorsection, the opposing surface of the pointer can be detected as acircular shape.

It is to be noted that, while, in the modification 16 described above,the number of reception conductors to be connected to the differentialamplifier 386 is four, which is an even number, the number of receptionconductors to be connected is not limited to four or any even number.For example, the unit number of reception conductors to be connected maybe three or five, which are odd numbers. In this instance, the centrallydisposed reception conductor from among the selected odd receptionconductors is preferably connected to the ground or to a referencevoltage similarly as in the case of the modification 12 describedhereinabove. This is because, as previously described, where the pointeris not grounded sufficiently, part of current can be shunted through thecentrally disposed reception conductor to thereby prevent deteriorationof the detection sensitivity.

While, in the modification 16 described above, the reversed code C_(k)is supplied to the transmission conductors 12 having low indexes n whilethe spread code C_(k) is supplied to the transmission conductors 12having high indexes n, the present invention is not limited to thisconfiguration. For example, the spread code C_(k) may be supplied to thetransmission conductors 12 having low indexes n while the reversed codeC_(k) is supplied to the transmission conductors 12 having high indexesn. Similarly, while the reception conductors 14 having low indexes m areconnected to the “+” terminals of the differential amplifier 386 and thereception conductors 14 having high indexes m are connected to the “−”terminals to carry out differential amplification, alternatively thereception conductors 14 having low indexes m may be connected to the “−”terminals while the reception conductors 14 having high indexes m areconnected to the “+” terminals.

[Modification 17]

While, in the modification 16 described above, the spread codes C_(k)supplied from the spread code supplying circuit 21 and the reversedcodes C_(k) which are reversed codes of the spread codes C_(k) aresupplied to four adjacent transmission conductors such that the samesigns are positioned adjacent to each other, the present invention isnot limited to this configuration. For example, the spread code C_(k) orthe reversed code C_(k) may be supplied to the transmission conductorsY_(n) and Y_(n+3) which are positioned at the opposite ends of the fourtransmission conductors Y_(n) to Y_(n+3) positioned adjacent to eachother while the reversed code C_(k) or the spread code C_(k) is suppliedto the transmission conductors Y_(n+1) and Y_(n+2) which are centrallypositioned.

A configuration and operation of the modification 17 are described withreference to FIGS. 50A and 50B. FIG. 50A shows a general configurationof the present modification 17 and FIG. 50B illustrates a waveform of anoutput signal output from a differential amplifier in the modification17.

The modification 17 is different from the modification 16 describedabove in that the supply pattern of the spread codes C_(k) and thereversed codes C_(k) is “−++−” and that the detection pattern of thereception conductors 14 of 4-input 1-output differential amplifier 396is “−++−” disposed in the order from the smaller side of the index m ofthe reception conductors 14. Of the four reception conductors X_(m) toX_(m+3) positioned adjacent to each other, the reception conductorsX_(m+1) to X_(m+2) are connected to the “+” terminals of thedifferential amplifier 396 while the reception conductors X_(m) andX_(m+3) are connected to the “−” terminals of the differential amplifier396. Since the configuration and operation of the other part of themodification 17 are the same as those of the modification 16 describedhereinabove with reference to FIGS. 1 and 47A to 49, overlappingdescription of the same is omitted herein to avoid redundancy.

In the present modification 17, the spread codes C_(k) supplied from thespread code supplying circuit 21 shown in FIG. 1 are supplied to thetransmission conductors Y_(n+1) and Y_(n+2) positioned centrally amongthe four transmission conductors Y_(n) to Y_(n+3) selected by thetransmission conductor selection circuit 382, while the reversed codesC_(k) obtained by reversing the sign of the spread codes C_(k) aresupplied to the transmission conductors Y_(n) and Y_(n+3) positioned onthe opposite ends.

Next, displacement of output signals where reception conductors to beconnected to the four input terminals of the differential amplifier 396are switched is described with reference to FIG. 50B. It is to be notedthat, for the convenience of description, the four input terminals ofthe differential amplifier 396 are referred to as input terminals 396 ato 396 d in the order beginning with the input terminal connected to thereception conductor having the highest index m.

Where the reception conductor selection circuit 384 successivelyswitches the reception conductors 14 to be connected to the inputterminals 396 a to 396 d of the differential amplifier 396 in such amanner as described above, when the reception conductors connected tothe input terminals 396 a to 396 d of the differential amplifier 396 arepositioned so as to be not influenced by the pointer at all, the outputsignal from the differential amplifier 396 is 0 (see 390 a of FIG. 50B).

Then, since the reception conductors 14 connected to the differentialamplifier 396 are approached by the pointer 19 beginning with theright-most reception conductor 14 connected to the input terminal 396 aof the differential amplifier 396, the signal input to the “−” terminalof the differential amplifier 396 gradually decreases. As a result, theoutput signal from the differential amplifier 396 is deflected to thepositive side (see 390 b of FIG. 50B). Thereafter, when the receptionconductor selection circuit 384 further switches the receptionconductors 14 to be connected to the differential amplifier 396, thereception conductors 14 connected to both of the input terminals 396 a(“−”) and 396 b (“+”) of the differential amplifier 396 are approachedby the pointer 19. Consequently, the signal input to the “−” terminalsgradually increases while the signal input to the “+” terminalsgradually decreases, and therefore, the output signal from thedifferential amplifier 396 is deflected to the negative side (see 390 cof FIG. 50B).

Then, as the reception conductor selection circuit 384 successivelyswitches the reception conductors 14 to be connected to the inputterminals 396 a to 396 d of the differential amplifier 396, thereception conductors 14 connected to the input terminals 396 a and 396 bof the differential amplifier 396 are gradually moved away from thepointer 19 and the reception conductor 14 connected to the inputterminal 396 c of the differential amplifier 396 is gradually approachedby the pointer 19 instead. As a result, the signal input to the “+”terminals of the differential amplifier 396 gradually decreases whilethe signal input to the “−” terminals of the differential amplifier 396gradually increases. Consequently, the output signal from thedifferential amplifier 396 further decreases. Then, when the pointer 19is positioned between the reception conductors 14 connected to the inputterminals 396 b and 396 c, the signal level of the signal output fromthe differential amplifier 396 becomes the lowest (see 390 d of FIG.50B).

Then, when the reception conductor selection circuit 384 furtherswitches the reception conductors 14 to be connected to the inputterminals 396 a to 396 d of the differential amplifier 396, thereception conductors 14 connected to the input terminals 396 a, 396 band 396 c of the differential amplifier 396 are gradually moved awayfrom the pointer 19 while the reception conductor 14 connected to theinput terminal 396 d of the differential amplifier 396 is approached bythe pointer 19. Consequently, the signal input to the “+” terminals ofthe differential amplifier gradually increases. As a result, the outputsignal from the differential amplifier 396 is deflected to the positiveside (see 390 e of FIG. 50B). Then, when the reception conductor 14connected to the input terminal 396 d of the differential amplifier 396comes closest to the pointer 19, the output signal from the differentialamplifier 396 exhibits the highest level (see 390 f of FIG. 50B).

Thereafter, when the reception conductor selection circuit 384 furthercarries out switching of the reception conductors to be connected to theinput terminals 396 a to 396 d of the differential amplifier 396, sinceall of the reception conductors connected to the input terminals 396 ato 396 d of the differential amplifier 396 are now moved away from thepointer 19, the signal input to the input terminals of the differentialamplifier 396 gradually increases. Then, when the reception conductorsconnected to the input terminals 396 a to 396 d of the differentialamplifier 396 are switched to those reception conductors which arepositioned so as not to be influenced by the pointer 19, the outputsignal from the differential amplifier 396 decreases to zero (see 390 gof FIG. 50B).

The output signal from the differential amplifier 396 thus exhibits sucha level variation as indicated by the curve 390 illustrated in FIG. 50B.It is to be noted that the output signal from the differential amplifier396 and the value obtained by integration of the output signalillustrated in FIG. 50B represent an output characteristic where thepointer 19 is placed at the cross point between the transmissionconductor 12 to which the spread code C_(k) is supplied and thereception conductor 14. Where the pointer 19 is placed at the crosspoint between the transmission conductor 12 to which the reversed codeC_(k) is supplied and the reception conductor 14 (for example, at thecross point between the transmission conductor Y_(n) and the receptionconductor X_(m+1)), the output signal from the differential amplifier396 exhibits a characteristic opposite to the output characteristicdescribed above.

In the illustrated example, the spread code C_(k) supplied from thespread code supplying circuit is supplied to the transmission conductorsY_(n+1) and Y_(n+2) positioned centrally among the four transmissionconductors Y_(n) to Y_(n+3) selected by the transmission conductorselection circuit 382, while the reversed code C_(k) obtained byreversing the sign of the spread code C_(k) is supplied to thetransmission conductors Y_(n) and Y_(n+3) positioned at the oppositeends. The reception conductors X_(m+1) and X_(m+2) centrally positionedamong the four reception conductors positioned adjacent to each otherare connected to the “+” terminals of the 4-input 1-output differentialamplifier 396, while the reception conductors X_(m) and X_(m+3) areconnected to the “−” terminals of the differential amplifier 396. Thus,an output signal similar to that obtained by carrying out an integrationprocess is obtained as an output signal from the differential amplifier396. Therefore, if the detection pattern of the present modification 17is adopted, then there is no necessity to carry out an integrationprocess, and consequently, accumulation of noise which may possiblyoccur when an integration process is carried out is eliminated. Further,since the differential amplification process is carried out, the noiseresisting property can be further improved.

Since the present modification 17 is configured such that the number ofoutput signals from a number of reception conductors 14 equals the totalnumber of the transmission conductors 12 to which the same spread codeor the reversed code having the sign reversed from the spread code issupplied, similarly to the modification 14, the minimum detection areaS_(min) on the sensor section becomes a square shape. As a result, anisotropic sensitivity distribution can be achieved in the minimumdetection area on the sensor section. In this instance, for example,even if a pointer having a circular opposing surface is disposed on thesensor section, the opposing surface of the pointer can be detected as acircular shape.

While, in the foregoing description, the number of reception conductorsto be connected to the differential amplifier is four, which is an evennumber, the present invention is not limited to this configuration. Forexample, the number of reception conductors 14 to be connected to thedifferential amplifier may be set to three or five, which are oddnumbers.

[Modification 18]

While, in the modification 17 described above, the supply pattern of thespread codes and the reversed codes of the spread codes and thedetection pattern of signals from the reception conductors are set to“−++−,” the supply pattern of the spread codes and the reversed codes ofthe spread codes and the detection pattern of signals from the receptionconductors may be set alternatively to “+−−+.” In the following, themodification 18 is described in reference to FIG. 51, wherein the spreadcodes and the reversed codes of the spread codes are set to and suppliedin the “+−−+” supply pattern, and the detection pattern is also set to“+−−+” such that the reception signals are differentially amplified by adifferential amplifier.

If the present modification 18 is compared with the modification 17,then it is different in that the inverter 381 which reverses the sign ofthe spread code C_(k) to be supplied from the spread code supplyingcircuit 21 to the transmission conductors is disposed such that thereversed signal is supplied to the two centrally located transmissionconductors Y_(n+1) and Y_(n+2) among the four transmission conductorsY_(n) to Y_(n+3) to be selected by the transmission conductor selectioncircuit 382. Another difference is that the polarities of the four inputterminals of a differential amplifier 397 are set to “+−−+” beginningwith the reception conductor 14 having the highest index m. The otherpart of the modification 18 is the same as that of the modification 17described hereinabove with reference to FIG. 50.

With the configuration of the modification 18, similar effects to thoseof the modification 17 are achieved. In particular, since there is nonecessity to provide an integration process, accumulation of noise whichis likely to occur when an integration process is carried out iseliminated. Also, since a differential amplification process is carriedout, the noise resisting property can be further improved. Furthermore,since the total number of transmission conductors 12 to which the samespread code or the reversed code obtained by reversing the sign of thespread code is supplied equals the number of output signals from anumber of reception conductors, the minimum detection area S_(min) onthe sensor section becomes a square shape. As a result, an isotropicsensitivity distribution can be achieved in the minimum detection areaon the sensor section. In this instance, for example, even if a pointerhaving a circular opposing surface is disposed on the sensor section,the opposing surface of the pointer can be detected as a circular shape.

In the modifications 16 to 18 described hereinabove with reference toFIGS. 47A to 51, the number of transmission conductors and the number ofreception conductors to be selected by the transmission conductorselection circuit and the reception conductor selection circuit,respectively, are set to an even number. In a modification 19 describedbelow, the number of transmission conductors and reception conductors tobe selected is set to an odd number as shown in FIGS. 52 to 54. It is tobe noted that, in the modifications 19 and 20 described below, thereception conductor array 13 includes 130 reception conductors 14.

[Modification 19]

First, a configuration of a modification 19 is described with referenceto FIG. 52. FIG. 52 schematically shows a general configuration of apointer detection apparatus wherein a 3-input 1-output differentialamplifier is used for the amplification circuit 32 (shown in FIG. 1).

First, a general configuration of the modification 19 is described withreference to FIGS. 1 and 52. The transmission section 200 shown in FIG.1 includes a spread code supplying circuit 21 for supplying spread codesC_(k), a transmission conductor selection circuit 402 for selectivelysupplying the spread codes C_(k) supplied from the spread code supplyingcircuit 21 to the transmission conductors 12, and an inverter 401provided between the spread code supplying circuit 21 and thetransmission conductor selection circuit 402 for inverting the spreadcode C_(k) supplied from the spread code supplying circuit 21 to produceand output a reversed code C_(k) . The spread code C_(k) and thereversed code C_(k) are supplied to three transmission conductors Y_(n)to Y_(n+2) positioned adjacent to each other by the transmissionconductor selection circuit 402. In particular, a spread code C_(k)supplied from the spread code supplying circuit 21 is supplied to thetwo transmission conductors Y_(n) and Y_(n+2) through the transmissionconductor selection circuit 402. Further, the spread code C_(k) isinverted into the reversed code C_(k) by the inverter 401 and thensupplied to the transmission conductor Y_(n+1) through the transmissionconductor selection circuit 402. In particular, in FIG. 52, the spreadcode supply pattern is “+−+.” It is to be noted that the configurationof the other part of the transmission section 200 in the presentmodification 19 is the same as that in the first embodiment describedhereinabove with reference to FIG. 1, and overlapping description of thesame is omitted herein to avoid redundancy.

Next, details of the transmission conductor selection circuit 402 aredescribed with reference to FIG. 53.

The transmission conductor array 11 is divided into 16 transmissionblocks 403 each including six transmission conductors positionedadjacent to each other, and includes a number of switch groups 402 aequal to the number of transmission blocks 403, that is, 16 switchgroups 402 a. In each of the transmission blocks 403, those twotransmission conductors 12 which have relatively high indexes n amongthe six transmission conductors 12 which form the transmission block 403are used commonly by another adjacent transmission block 403. Inparticular, as seen in FIG. 53, from among the transmission conductorsY_(n) to Y_(n+5) which form the transmission block 403, those twotransmission conductors Y_(n+4) and Y_(n+5) having relatively highindexes are used commonly by an adjacent transmission block.

Each of the switch groups 402 a includes three switches 402 a ₁, 402 a ₂and 402 a ₃. Six terminals 402 b of each of the switch groups 402 a onthe output side are connected respectively to the correspondingtransmission conductors Y_(n) to Y_(n+5). Further, input terminals 402 cof the switches 402 a ₁ and 402 a ₃ among the three switches 402 a ₁,402 a ₂ and 402 a ₃ are connected to the spread code production circuit24 shown in FIGS. 1 and 3, which provide spread codes C₁ to C₁₆. Theinput terminal 402 c of the switch 402 a ₂ is connected to the spreadcode production circuit 24, which provides the spread codes C₁ to C₁₆,through the inverter 401.

As seen in FIG. 53, for example, the switch group 402 a, to which thespread code C_(k) and the reversed code C_(k) of the spread code C_(k)are supplied, supplies the spread code C_(k) to the transmissionconductors Y_(n) and Y_(n+2) and supplies the reversed code C_(k) to thetransmission conductor Y_(n+1). Then, after the spread code C_(k) andthe reversed code C_(k) are supplied for a predetermined period of time,the switch group 402 a switches the transmission conductors 12 to beconnected to the spread code production circuit 24 so that the spreadcode C_(k) is supplied to the transmission conductors Y_(n+1) andY_(n+3) and the reversed code C_(k) is supplied to the transmissionconductor Y_(n+2). Thereafter, the switch group 402 a successively andtime-dependently switches the transmission conductors to be connected tothe spread code production circuit 24. Then, after the spread code C_(k)is supplied to the transmission conductors Y_(n+5) and Y_(n+3) and thereversed code C_(k) is supplied to the transmission conductor Y_(n+4),the switch group 402 a supplies the spread code C_(k) again to thetransmission conductors Y_(n) and Y_(n+1) and supplies the reversed codeC_(k) again to the transmission conductor Y_(n+1). Thereafter, thesequence of operations described above is repeated. In this manner, thespread code C_(k) supplied from the spread code supplying circuit 21 andthe reversed code C_(k) of the spread code C_(k) are supplied to all ofthe transmission conductors 12 which form the transmission conductorarray 11.

Next, details of a reception conductor selection circuit 813 in themodification 19 are described with reference to FIGS. 1, 52 and 54. Asseen in FIG. 54, the reception section 320 in the present modification19 includes a reception conductor selection circuit 813, anamplification circuit 32, an A/D conversion circuit 33, a correlationvalue calculation circuit 34 and a position detection circuit 35.

The reception conductor array 13 is divided into 43 detection blocks336. Each of the detection blocks 336 includes three receptionconductors X_(m) to X_(m+2) positioned adjacent to each other, that is,having consecutive indexes m. The reception conductors X_(m) to X_(m+2)which form each of the detection blocks 336 are used commonly by anotheradjacent detection block 336. In particular, in the present modification19, the reception conductor array 13 is divided into detection blocks{X₁ to X₃}, {X₂ to X₄}, . . . , {X₁₂₇ to X₁₂₉} and {X₁₂₈ to X₁₃₀}.

The reception conductor selection circuit 813 includes a switch group815 including three switches. The switch group 815 has input terminals815 a respectively connected to corresponding reception conductors 14.The switch group 815 has output terminals 815 b connected to inputterminals of I/V conversion circuits 32 a. The switch group 815successively switches the detection block 336 to be connected to the I/Vconversion circuits 32 a at predetermined intervals of time. Inparticular, if it is assumed that the detection block {X₁ to X₃} arefirst connected to the I/V conversion circuits 32 a at the succeedingstage, then the detection block {X₂ to X₄} are next connected to the I/Vconversion circuits 32 a at a next interval of time. Thereafter, thereception conductor selection circuit 813 successively switches thedetection block 336 at predetermined intervals of time, and then, afterthe last detection block {X₁₂₈ to X₁₃₀} is connected to the I/Vconversion circuits 32 a, the reception conductor selection circuit 813again connects the first detection block {X₁ to X₃} to the I/Vconversion circuits 32 a. Thereafter, the sequence of operationdescribed above is repeated. Then, output signals from the receptionconductors 14 are converted into voltage signals by the I/V conversioncircuits 32 a and input to a differential amplifier 405.

The amplification circuit 32 is formed of three I/V conversion circuits32 a and a differential amplifier 405. Output terminals of the I/Vconversion circuits 32 a are respectively connected to different inputterminals of the differential amplifier 405. Here, the I/V conversioncircuits 32 a are connected in the following manner. In particular, theI/V conversion circuit 32 a connected to the reception conductor X_(m)having the lowest index m and the I/V conversion circuit 32 a connectedto the reception conductor X_(m+2) having the highest index m areconnected to non-negated (+) input terminals of the differentialamplifier 405, while the remaining I/V conversion circuit 32 a isconnected to a negated (−) input terminal of the differential amplifier405.

The differential amplifier 405 is a 3-input 1-output differentialamplifier. The three input terminals of the differential amplifier 405are set such that the polarity of those input terminals, to which thereception conductor X_(m) having the lowest index m and the receptionconductor X_(m+2) having the highest index m among the three receptionconductors X_(m) to X_(m+2) selected by the reception conductorselection circuit 813 are connected, is “+.” The polarity of theremaining input terminal, to which the remaining reception conductorX_(m+1) is connected, is “−.” The differential amplifier 405 isconfigured such that the amount of amplification it applies to a signalinput from the “−” input terminal is twice as much as the amount ofamplification it applies to a signal input to the “+” input terminal.This way, since a single reception conductor 14 is connected to the “−”terminal of the differential amplifier 405 in the present modification19 while two reception conductors 14 are connected to the “+” terminalsof the differential amplifier 405, the levels of thedifferentially-amplified signals become equal to each other, or in otherwords, the output signal of the differential amplifier becomes zero(canceled out). The differential amplifier 405 differentially amplifiesoutput signals from the reception conductors 14 and outputs a resultingsignal to the A/D conversion circuit 33 at the succeeding stage. It isto be noted that, in FIG. 54, a plurality of I/V conversion circuits 32a and a plurality of switch groups 815 are omitted in order to simplifythe illustration. Further, since the configuration of the other part ofthe reception section 320 is the same as that of the first embodimentdescribed hereinabove with reference to FIG. 1, overlapping descriptionof the same is omitted herein to avoid redundancy.

The reception conductor selection circuit 813 carries out selectiveswitching similar to those in the modification 4 illustrated in FIG. 31and the modification 16 illustrated in FIG. 49. In particular, theswitch group 815 of the reception conductor selection circuit 813connects the reception conductors X_(m) and X_(m+2) to the “+” terminalsof the differential amplifier 405, and connects the reception conductorX_(m+1) to the “−” terminal of the differential amplifier 405 in theorder beginning with the reception conductors X₁ to X₃ having the lowestindexes as seen in FIG. 54. In short, the two “+” terminals of thedifferential amplifier 405 are connected to the reception conductors X₁and X₃ and the “−” terminal of the differential amplifier 405 isconnected to the reception conductor X₂. Then, after a predeterminedinterval of time elapses, the switch group 815 of the receptionconductor selection circuit 813 switches to the reception conductorspositioned in the direction in which the index m increases, from thereception conductors 14 previously connected to the differentialamplifier 405, that is, the reception conductors X₂ and X₄ are newlyconnected to the “+” terminals of the differential amplifier 405 and thereception conductor X₃ is newly connected to the “−” terminal of thedifferential amplifier 405. Then, after the switching, new outputsignals are obtained from the reception conductors X₂ to X₄ connected tothe switch group 815. Thereafter, the switch group 815 of the receptionconductor selection circuit 813 successively switches the receptionconductors 14 to be connected to the differential amplifier 405 atpredetermined intervals of time. Then, after the last group of receptionconductors X₁₂₈ to X₁₃₀ to be connected to the differential amplifier405 are so connected, the switch group 815 of the reception conductorselection circuit 813 returns to the initial state, that is, the stateillustrated in FIG. 54. Thereafter, the sequence of operations describedabove is repeated.

Then, upon such switching as described above, the differential amplifier405 differentially amplifies an output signal input thereto from thereception conductors X_(m) and outputs a resulting signal to the A/Dconversion circuit 33 at the succeeding stage (see FIG. 1). Thereafter,the output signal digitally converted by the A/D conversion circuit 33is subjected to correlation calculation by the correlation valuecalculation circuit 34, and a correlation value which results from thecorrelation calculation is stored in the correlation value storagecircuit 34 d (see FIG. 8).

Where the detection pattern of output signals is set to “+−+” as in thepresent modification 19, the polarity of the three input terminals ofthe differential amplifier 405 is leftwardly and rightwardly symmetricalwith respect to the polarity of the central input terminal. Therefore,similarly as in the modification 17, a result similar to the resultobtained by carrying out an integration process upon position detectioncan be obtained, as illustrated in FIG. 50B. Accordingly, in the presentmodification 19, similar effects to those achieved by the modification17 can be achieved. In particular, since there is no necessity toprovide an integration circuit at the succeeding stage, accumulation ofnoise which is likely to occur where an integration process is carriedout is eliminated. Additionally, since a differential signal process isinvolved, the noise resisting property can be further improved.

In the present modification 19, the number of signals from a number ofreception conductors 14 equals the total number of the transmissionconductors 12 to which the same spread code C_(k) or the reversed codeC_(k) having the sign reversed from the spread code C_(k) is supplied,similarly as in the modifications 14 and 17. Thus, an isotropicsensitivity distribution can be obtained in the minimum detection areaon the sensor section 100. In this instance, for example, even if apointer having a circular opposing surface is disposed on the sensorsection, the opposing surface of the pointer can be detected as acircular shape.

[Modification 20]

While, in the modification 19, the supply pattern and the detectionpattern of spread codes are “+−+,” they may alternatively be “−+−.” Inthe following, a modification 20 wherein the detection pattern is set to“−+−” is described.

A general configuration of the present modification 20 is described withreference to FIG. 55. If the present modification 20 is compared withthe modification 19 described hereinabove with reference to FIG. 52,then it has the following differences. In particular, two inverters 406for inverting the spread code C_(k) supplied from the spread codesupplying circuit 21 and outputting a resulting reversed code C_(k) areinterposed between the spread code supplying circuit 21 and thetransmission conductor selection circuit 402. The reversed code C_(k) issupplied to the transmission conductors Y_(n) and Y_(n+2) positioned onthe opposite ends among the three transmission conductors Y_(n) toY_(n+2) selected by the transmission conductor selection circuit 402.The polarity of the three input terminals of a 3-input 1-outputdifferential amplifier 407 is set such that the polarity of those inputterminals connected to the reception conductor X_(m) having the lowestindex m and the reception conductor X_(m+2) having the highest index mamong the three reception conductors X_(m) to X_(m+2) selected by areception conductor selection circuit 813 is “−,” and the polarity ofthe input terminal to which the remaining one reception conductorX_(m+1) is connected is “+.” Since the configuration of the other partof the present modification 20 is the same as that of the modification19 described hereinabove, overlapping description of the sameconfiguration is omitted herein to avoid redundancy.

In the modification 20, the polarity of the three input terminals of thedifferential amplifier 407 is leftwardly and rightwardly symmetricalwith respect to the polarity of the central input terminal. Accordingly,in the present modification 20 also, a result similar to the resultobtained by carrying out an integration process upon position detectionas illustrated in FIG. 50B can be obtained. Accordingly, in the presentmodification 20 also, similar effects to those achieved by themodifications 17 and 19 can be achieved. In particular, since there isno necessity to provide an integration process, accumulation of noisewhich is likely to occur where an integration process is carried out iseliminated. Additionally, since a differential signal process isinvolved, the noise resisting property can be further improved.

8. Eighth Embodiment Detection of Hovering

The pointer detection apparatus to which the present invention isapplied not only may be incorporated in a liquid crystal displayapparatus, but also may be formed as a stand-alone pointer detectionapparatus separate from a liquid crystal display apparatus. Thestand-alone application is similar to an existing position detectionapparatus that incorporates an electromagnetic induction system, forexample.

A liquid crystal display apparatus which incorporates an existingpointer detection apparatus is usually formed such that the detectionarea of the pointer detection apparatus and the display area of theliquid crystal display apparatus overlap with each other. Therefore, auser can point to a desired position by pointing, by means of a pointersuch as a finger, to a position at which an object such as an icon or atool bar which the user wants to point to or select is displayed.

On the other hand, a pointer detection apparatus and a liquid crystaldisplay apparatus may also be formed as two separate devices, forexample, in the case of a touch pad or a digitizer of theelectromagnetic induction type, which is incorporated into an existingpersonal computer as the computer's input device. In such cases, it isdifficult for the user to intuitively grasp a relation between theposition pointed to on the input device and the position on the liquidcrystal display apparatus. Therefore, to allow a user to visuallyrecognize the correspondence between the position on the input devicethat the user is pointing to and the position on the liquid crystaldisplay apparatus, some of these existing input devices allow detectionof a pointer that is positioned merely in the proximity of the inputdevice, that is, the pointer that is not in direct contact with thedetection section of the input device but is “hovering” over thedetection section (this state is hereinafter referred to as a “hoveringstate”).

However, where the pointer is in a hovering state, that is, where thepointer is positioned a little above the surface of the sensor section100 (e.g., the second substrate 17 in FIG. 12A or 12B), the detectionsensitivity is rather low and, also, the influence of noise becomes moresignificant. Therefore, it is difficult to carry out an accurateposition detection of a pointer in a hovering state.

[Modification 21]

A modification 21 is directed to a discrimination technique suitable fordiscriminating (determining) with a higher degree of accuracy whether ornot a pointer is in a hovering state, and is described with reference toFIGS. 56A to 58. FIGS. 56A and 56B illustrate a state wherein a finger19 as a pointer touches the sensor section 100 as illustrated in FIG.12B and a level curve of a detection signal (correlation value) obtainedin this state, respectively. FIGS. 57A and 57B illustrate another statewherein the finger 19 is spaced above the sensor section 100, that is,in a hovering state, and a level curve of a detection signal(correlation value) obtained in this state, respectively. FIG. 58illustrates a map showing a distribution of level values of thedetection signals (correlation values) obtained, at a certain point oftime, over a region in the proximity of a cross point that is in thestate illustrated in FIG. 57A. In the following, a state wherein thefinger 19 touches is compared with another state wherein the finger 19does not touch, that is, wherein the finger 19 is in a hovering state.

First, in the state wherein the finger 19 touches the surface of thesensor section 100 as seen in FIG. 56A, part of an electric fieldemerging from a transmission conductor 12 converges to the finger 19 andpart of the current flowing from the transmission conductor 12 to areception conductor 14 is shunted to the ground through the finger 19,as described hereinabove in the description of the first embodiment withreference to FIGS. 12A and 12B. As a result, since the current flowinginto the reception conductor 14 decreases, the signal level indicated bya level curve 420 increases steeply in the region contacted by thefinger 19, in comparison to the other region that is not contacted bythe finger 19, and the signal level exhibits a peak 420 a in the regioncontacted by the finger 19 as seen in FIG. 56B.

In contrast, in the state wherein the finger 19 does not touch thesurface of the sensor section 100 (in a hovering state) as seen in FIG.57A, very small part of an electric field emerging from the transmissionconductor 12 converges to the finger 19, so that only a portion of thecurrent flowing from the transmission conductor 12 to the receptionconductor 14 is shunted to the ground through the finger 19. As aresult, the current flowing into the reception conductor 14 decreases bya small amount. Therefore, a level curve 421 still exhibits the highestsignal level in a region where the finger 19 is positioned most closelyto the surface of the sensor section 100, shown as a peak 421 a in FIG.57B, but the value of the peak 421 a is lower than that of the peak 420a exhibited when the finger 19 is touching the sensor section 100 (FIG.56B). Consequently, the level curve 421 indicates a broadened(flattened) form as seen in FIG. 57B.

In the hovering state discrimination technique in the presentmodification 21, a ratio between a gradient of an edge and a peak valueof the level curve is determined and is compared with a predeterminedthreshold value to determine whether or not the finger 19 is in ahovering state.

FIG. 58 is a distribution map of level values of the detection signal(correlation values) obtained at a certain point of time in a region inthe proximity of a cross point over which the finger 19 is positioned.It is to be noted that FIG. 58 illustrates level values obtained at 3×3cross points and the values are in a normalized form. The ratio betweenthe peak value and the gradient of the edge is calculated, and theresulting ratio is compared with a predetermined threshold value, forexample, 0.7.

In the example illustrated in FIG. 58, a maximum value “100” of thelevel is obtained at the central cross point, and another level value“50” is obtained at cross points at the positions leftwardly,rightwardly, upwardly and downwardly of the central cross point. Thegradient of the edge of the level curve 421 of the detection signal(correlation value) can be obtained by determining the differencebetween the peak value, which is indicated by the length of adouble-sided arrow mark in FIG. 57B (i.e., the level value “100” in thecentral grid of FIG. 58), and the level value at a cross point adjacentto the cross point at which the peak value is obtained (e.g., the levelvalue “50” adjacent to the central grid of “100” in FIG. 57B). Forexample, in the case of FIGS. 57A and 57B, since the peak value of thelevel curve is “100” at the central grid of FIG. 58, the gradient of theedge can be calculated as 100−50=50. Accordingly, the ratio between thegradient of the edge and the peak value of the level curve is (gradientof the edge/peak value)=50/100=0.5. Thus, in this example based on thelevel values illustrated in FIG. 58, it is determined that the pointer19 is in a hovering state. On the other hand, if the ratio between thegradient of the edge and the peak value of the level curve 421 is higherthan a predetermined threshold value (for example, 0.9), it isdetermined that the pointer 19 is in a state wherein it is touching thesurface of the sensor section 100.

While, in the description of the example illustrated in FIG. 58, onepredetermined threshold value is used for determining the presence orabsence of a hovering state, the present invention is not limited tothis configuration. For example, it is possible to provide a secondthreshold value lower than the predetermined threshold value such thatthe ratio between the gradient of the edge and the peak value of thelevel curve is compared additionally with the second threshold value tomore precisely determine the degree of the hovering state, such as thedistance between the sensor section and the pointer.

It is to be noted that, in the discrimination technique described above,though not shown in the figure, the calculation may be carried out, forexample, by the position detection circuit 35 provided in the receptionsection 300 shown in FIG. 1 or by an external computer.

While, in the modification 21 described hereinabove, the discriminationof a hovering state is carried out directly based on the level curve ofthe detection signal, that is, based on the mapping data of the levelvalues, the present invention is not limited to this configuration. Thelevel curve of the detection signal may be subjected to a suitablenonlinear process such that a hovering state can be determined based onthe characteristic obtained by the nonlinear process.

For example, logarithmic conversion may be carried out as a nonlinearprocess for the level curve of the detection signal (correlation value).Where nonlinear process is not carried out, the level of the detectionsignal obtained when the pointer 19 is touching the surface of thesensor section 100 can be extremely high at a location at which thepointer 19 touches the sensor section 100, while the level of thedetection signal can be extremely low at another portion at which thepointer 19 is spaced away from the surface of the sensor section 100.Therefore, since the level of the detection signal exhibits an extremedifference between the two cases described above (and is extremely lowwhere the pointer 19 is spaced away from the sensor section), it isdifficult to accurately recognize a state wherein the pointer 19 isspaced only slightly from the surface of the sensor section 100.

If a predetermined signal conversion such as, for example, a logarithmicconversion is carried out for the level curve of the detection signals(correlation values), then it is possible to make a signal portion of arelatively low level in the detection signal more conspicuous whilesuppressing a signal portion having a relatively high level. In otherwords, the shape of the peak portion of the level curve after thelogarithmic conversion is broadened (flattened) and the maximum valuethereof is suppressed. This way, the transition of the level value nearthe boundary between the touched state and the non-touched (hovering)state of the pointer becomes continuous, and a hovering state can bereadily recognized even if the hovering state is such that the pointer19 is spaced only slightly from the sensor section 100. Consequently,the recognition characteristic of the pointer detection apparatus can beimproved.

[Modification 22]

Next, an example of a configuration wherein position detection of apointer can be carried out with certainty even where the pointer is in ahovering state is described with reference to FIGS. 59 and 60.

FIG. 59 illustrates a concept of a relationship between a supply patternof a spread code C_(k) and a detection pattern of an output signal in aminimum detection area S₁ where a pointer 19 is positioned in theproximity of the sensor section 100 (see FIG. 1). FIG. 60 illustrates aconcept of another relationship between a supply pattern of a spreadcode C_(k) and a detection pattern of an output signal in a minimumdetection area S₂ where the pointer 19 is positioned relatively fartheraway from the sensor section 100.

First, a switching operation regarding how many conductors are to beselected, i.e., a switching operation of the “selection number” oftransmission conductors 12 and reception conductors 14 is described. Theswitching of the selection number is carried out based on a decisionregarding whether or not the pointer 19 is in a hovering state, asdescribed, for example, in the foregoing description of the modification21. In particular, the ratio between the gradient of the edge and thepeak value of a level curve is determined, and the determined ratio iscompared to a predetermined threshold value to determine whether or notthe pointer 19 is in a hovering state. If it is determined that thepointer 19 is in a hovering state, then the transmission conductorselection circuit and the reception conductor selection circuit shown inFIG. 1 are controlled so that a plurality of transmission conductors 12and a plurality of reception conductors 14 are selected. Thedetermination of a hovering state is carried out, for example, by theposition detection circuit 35 described hereinabove with reference toFIGS. 1, 39 and so forth, and when it is determined that the pointer 19is in a hovering state, the position detection circuit 35 outputs apredetermined signal to the control circuit 40 described hereinabovewith reference to FIG. 1 and so forth. Then, when a predetermined signalis input from the position detection circuit 35, the control circuit 40controls the transmission conductor selection circuit 22 and thereception conductor selection circuit 31 so that a predetermined spreadcode C_(k) is supplied to a plurality of transmission conductors 12 anda correlation value is calculated based on output signals from aplurality of reception conductors 14.

Next, details of the switching operation described above are described.In the following description, it is assumed that a spread code C_(k) canbe supplied to a plurality of transmission conductors Y_(n) and anamplifier (432/532) having a plurality of input terminals whose polarityis “+” is used for the amplification circuit 32 of the reception section300, such that an output signal of an arbitrary reception conductorX_(m) is detected by the amplifier 432/532.

First, as seen in FIG. 59, when the pointer 19 touches the surface ofthe sensor section 100, the spread code C_(k) is supplied to twotransmission conductors Y_(n+1) and Y_(n+2), and the amplifier 432provided in the amplification circuit 32 of the reception section 300amplifies and outputs output signals from two reception conductorsX_(m+1) and X_(m+2).

Then, if the pointer 19 such as a finger is spaced from the surface ofthe sensor section 100, then since the ratio between the gradient of theedge and the peak value of the level curve becomes lower than apredetermined threshold value, it is determined that the pointer 19 isin a hovering state. Consequently, the control circuit 40 controls thetransmission conductor selection circuit 22 and the reception conductorselection circuit 231 (see FIG. 39) based on a predetermined signalreceived from the position detection circuit 35, to connect the spreadcode supplying circuit 21 and the transmission conductor array 11 sothat the spread code C_(k) is supplied to the four transmissionconductors Y_(n) to Y_(n+3). Similarly, the control circuit 40 controlsthe reception conductor selection circuit 231 to connect the fourreception conductors X_(m) to X_(m+3) to the input terminals of theamplifier 532 provided in the amplification circuit 32. Consequently,the detection area changes from a detection area S₁ in the state whereinthe pointer 19 touches the surface of the sensor section 100 as seen inFIG. 59, to another detection area S₂ having a broader range fordetection as seen in FIG. 60.

In this instance, the supply pattern of the spread code C_(k) in thetransmission section 200 and the detection pattern of a signal in thereception section 300 may be, for example, “++” or “+−.”

As described hereinabove, in the present modification 22, where it isdetermined that the pointer 19 is in a hovering state, control iscarried out so as to increase the number of transmission conductors 12and reception conductors 14 so that the number of transmissionconductors 12 to which the same spread code C_(k) is to be supplied andthe number of reception conductors 14 to be connected to the amplifierat the same time are increased, thereby enhancing the detectionsensitivity. This makes it possible to carry out position detection ofthe pointer 19 in a hovering state with a higher degree of certainty.

While, in the present modification 22 described above, the number oftransmission conductors and reception conductors to be selected isadjusted to two or four in response to a determined state of a pointer,the present invention is not limited to this configuration. For example,the number of transmission conductors and reception conductors to beselected can be set arbitrarily. As a specific example, a plurality ofthreshold values for a peak value of the detection signal may be set inadvance such that a peak value is compared with the plurality ofthreshold values and the number of transmission conductors and receptionconductors to be selected can be gradually increased as the peak valuedecreases successively below the threshold values. Further, the numberof transmission conductors to be selected and the number of receptionconductors to be selected need not be equal to each other. Stillfurther, the adjustment of the numbers of transmission conductors 12 andreception conductors 14 to be selected need not be carried out for bothof the transmission conductors 12 and the reception conductors 14, butmay be carried out only for the transmission conductors 12 or for thereception conductors 14.

The pointer detection apparatus periodically carries out a detectionprocess, that is, scanning, of a variation of current over all crosspoints on the sensor section in order to detect a pointer even when nopointer is touching the pointer detection apparatus, for example, inorder to immediately detect a pointer such as a finger (see FIG. 18). Itis to be noted that, in the following description, to carry out adetection operation using all of the transmission conductors and thereception conductors is referred to as “all scanning.” For all scanning,a high detection sensitivity and a high speed are demanded so that apointer can be detected immediately and with certainty.

However, if all scanning is carried out for the transmission conductorsand the reception conductors per (in the unit of) one conductor or asmall number of conductors at a time, a large number of points need tobe scanned and a longer period of time is required to complete the allscanning.

[Modification 23]

In the following, a method of carrying out the all scanning with a highsensitivity and at a higher speed is described. Further, if an outputsignal is not detected from the sensor section, the number oftransmission conductors and reception conductors to be used in a singlecycle of a detection process (that is, the size of a minimum detectionarea) is increased so as to enlarge the detection area.

It is to be noted that the number of conductors to be selected can beset arbitrarily in response to the size of the sensor section, arequired sensitivity, a desired detection speed, and so forth.

Those conductors whose number is to be increased or decreased may beboth of the transmission conductors and the reception conductors oreither the transmission conductors alone or the reception conductorsalone. It is to be noted that, where the numbers of both of thetransmission conductors and the reception conductors are to be increasedor decreased, the numbers may be different from each other. Further,according to the present invention, various methods can be applied aslong as the methods increase or decrease the effective area of thedetection area for which signal detection is carried out.

It is to be noted that the number of transmission conductors andreception conductors to be used may be varied based not only on thepresence or absence of a detection signal but also on the level of thedetection signal. For example, when the level of the detection signal ishigher than a predetermined threshold value set in advance, the numberof conductors may be decreased, but when the level of the detectionsignal is lower than the predetermined threshold value, the number ofconductors may be increased. Not one but two or more threshold valuesmay be set. As the method of detecting the level of the detectionsignal, the technique described hereinabove in connection with themodification 21 with reference to FIGS. 56A to 58 may be used.

With the present modification 23, when a detection signal cannot beobtained from the sensor section, the all scanning can still beimplemented with a high sensitivity and at a high speed by increasingthe number of transmission conductors and reception conductors to beused for detection of a pointer to thereby expand the detection area.

[Modification 24]

In the first embodiment described hereinabove, the sensor section 100includes the reception conductors 14 provided in the proximity of thedetection surface, that is, adjacent to the second substrate 17 asdescribed hereinabove with reference to FIG. 2. Since, in the sensorsection 100 according to the first embodiment, the transmissionconductors 12 are disposed at a position farther than the receptionconductors 14 from the pointer 19, an electric field emerging from thetransmission conductors 12 converges to the pointer 19 in a wider(expanded) path than an electric field which converges to the receptionconductors 14, as seen in FIG. 12B. Therefore, even an electric fieldfrom a transmission conductor 12 on the outer side in the extensiondirection of the reception conductors 14 with respect to the position atwhich the pointer 19 is actually positioned may converge to the pointer19.

In the following, this phenomenon is described with reference to FIG.61. In the following, it is assumed that the transmission conductorselection circuit and the reception conductor selection circuit selectfive transmission conductors Y_(n) to Y_(n+4) and five receptionconductors X_(m) to X_(m+4) at the same time to detect the pointer 19.

As seen in FIG. 61, the transmission conductor selection circuitsupplies a spread code C_(k) supplied from the spread code supplyingcircuit 21 to the transmission conductors Y_(n) to Y_(n+1) havingrelatively low indexes n among the selected five transmission conductorsY_(n) to Y_(n+4). Meanwhile, to the transmission conductors Y_(n+3) andY_(n+4) having relatively high indexes n, the reversed code C_(k)produced by inversion of the spread code C_(k) by means of an inverter431 is supplied. Further, the centrally located transmission conductorY_(n+2) is grounded.

Similarly, the reception conductor selection circuit connects thereception conductors X_(m+3) and X_(m+4) having relatively high indexesm among the selected reception conductors X_(m) to X_(m+4) to the inputterminals of the differential amplifier 430 whose polarity is “+,” andconnects the reception conductors X_(m) and X_(m+1) having relativelylow indexes m to the input terminals of the differential amplifier 430whose polarity is “−,” and further connects the centrally positionedreception conductor X_(m+2) to the ground. It is to be noted that, sincethe configuration of the other part of the present modification 24 isthe same as that of the modification 12 described hereinabove withreference to FIG. 40, overlapping description of the same configurationis omitted herein to avoid redundancy.

When, for example, a pointer 19 of a substantially circular shape (asolid line in FIG. 61) is placed, then electric fields emerging from thetransmission conductors Y_(n−1) and Y_(n+5), which are positionedadjacent to the transmission conductors Y_(n) to Y_(n+4) on which thepointer 19 is placed and thus are positioned on the outer sides of thetransmission conductors Y_(n) to Y_(n+4) in the direction in which thereception conductors 14 extend, are absorbed by the pointer 19 and thusdetected as indicated by a broken line in FIG. 61. This occurs moreconspicuously where the distance between the transmission conductors 12and the pointer 19 is relatively large, for example, where the spacer 16interposed between the transmission conductors 12 and the receptionconductors 14 is thick or where the pointer 19 to be detected is in ahovering state.

Therefore, in the present modification 24, in order to solve the problemdescribed above, the detection width of the transmission conductor array11, which is disposed relatively farther from the detection surface ofthe sensor section 100, is set relatively narrow while the detectionwidth of the reception conductor array 13, which is disposed relativelynearer to the detection surface, is set relatively wide so that, on thedetection surface, no difference will appear between the extent to whichthe level curve of the transmission signal supplied from thetransmission section expands (i.e., the detection width) and the extentto which the level curve of the reception signal input to the receptionsection expands.

[Modification 25]

FIG. 62 illustrates a relationship between a supply pattern of a spreadcode used by the transmission section and a detection pattern of asignal used by the reception section according to the modification 25.In the following, the modification 25 is described with reference toFIGS. 39 and 62. FIG. 62 illustrates the case where the number oftransmission conductors 12 to be selected by the transmission conductorselection circuit is reduced from five to three while the configurationof the other part is the same as that described hereinabove withreference to FIG. 61.

In the present modification 25, the reception conductor selectioncircuit 31 connects, for example, the reception conductors X_(m) andX_(m+1) and the reception conductors X_(m+3) and X_(m+4) positioned onthe opposite ends among five arbitrary reception conductors X_(m) toX_(m+4) positioned adjacent to each other to input terminals of adifferential amplifier. Also in the present modification 25, outputsignals from the reception conductors X_(m) and X_(m+1) selected by thereception conductor selection circuit 31 are converted into voltagesignals by the I/V conversion circuit 32 a (not shown) and supplied toinput terminals of the differential amplifier 430. However, this is thesame configuration as that of the modification 10 described hereinabovewith reference to FIG. 39, and therefore, the reception conductorselection circuit 231 and the I/V conversion circuit 232 a are notshown.

The transmission conductor selection circuit 22 selects three arbitrarytransmission conductors Y_(n+1) to Y_(n+3) positioned adjacent to eachother, and supplies a spread code to the transmission conductor Y_(n+1)having the lowest index m among the selected three transmissionconductors, and supplies a reversed code to the transmission conductorY_(n+3) having the highest index m, while it connects the centrallylocated transmission conductor Y_(n+2) to the ground.

Where the number of transmission conductors Y_(n) to be selected by thetransmission conductor selection circuit 22 is smaller than the numberof reception conductors X_(m) to be selected by the reception conductorselection circuit 231 as in this example, the spread of the level curveof the transmission signals by the transmission section 200 on thedetection surface becomes substantially the same as the spread of thelevel curve of the reception signals input to the reception section 310.In other words, the aperture ratio (aspect ratio) of the spread of thelevel curve by the transmission section 200 and the reception section310 can be made close to 1. As a result, even if a pointer having acircular opposing surface is disposed on the sensor section 100, theopposing surface of the pointer can be detected not as an elliptic shapeas indicated by a broken line in FIG. 61 but as a circular shape.

While, in the present modification 25 described above, the numbers oftransmission conductors and reception conductors to be selected aredifferent from each other so that the aperture ratio may become one, thepresent invention is not limited to this configuration. For example, theaperture ratio may be adjusted by making the shapes such as the widthsof the transmission conductors and the reception conductors differentfrom each other, or by making the arrangement patterns such as circularpatterns or conjoined hexagonal patterns of the conductors or thepitches between the conductors different from each other between thetransmission conductors and the reception conductors. Further, whileFIG. 61 shows an example wherein a differential amplifier is used forthe amplification circuit of the reception section, a single-inputamplifier may be used instead.

[Modification 26]

In the pointer detection apparatus 1 of the first embodiment describedhereinabove, an output signal output from an I/V conversion circuit 32 ais amplified by an amplifier (not shown) so that it has a predeterminedsignal level and then converted into a digital signal by the A/Dconversion circuit 33. The digital signal is then input to thecorrelation value calculation circuit 34 as seen in FIG. 1 so thatcorrelation calculation can be carried out.

In this instance, there is a problem that, where the noise is higherthan the reception signal, if the signal level of the output signal isalways amplified, then the noise is amplified together with thereception signal. Then, the A/D converter, to which the amplified noiseis input, clips the reception signal, resulting in failure ofappropriate detection of the reception signal.

On the other hand, if the signal level of an output signal is alwaysamplified, then when a pointer in a hovering state is to be detected,for example, as in the case of the modification 23, the change level(variation) of the reception signal becomes very low, making itdifficult to detect a pointer.

In the following, the modification 26 is described with reference toFIGS. 63 and 64. FIG. 63 shows a general block configuration of areception section 330 in the modification 26 and FIG. 64 shows a circuitconfiguration of an absolute value detection circuit which forms a gainvalue setting circuit hereinafter described. If the reception section330 in the present modification 26 is compared with the receptionsection 300 in the first embodiment described hereinabove with referenceto FIGS. 1, 6 and 8, then it is different in that a gain adjustmentcircuit 481 is provided in place of the amplifier (not shown) between anI/V conversion circuit 32 a of the amplification circuit 32 and the A/Dconversion circuit 33, and that a gain value setting circuit 482 isprovided. Since the configuration of the other part of the receptionsection 320 in the present modification 24 is the same as the receptionsection 300 in the first embodiment described hereinabove with referenceto FIG. 1, overlapping description of the same configuration is omittedherein to avoid redundancy.

The gain adjustment circuit 481 is provided in order to increase ordecrease the signal level of a signal input thereto according to apredetermined signal level. The gain adjustment circuit 481 is providedbetween the I/V conversion circuit 32 a of the amplification circuit 32and the A/D conversion circuit 33 and carries out predetermined signallevel variation based on a control signal from the gain value settingcircuit 482 hereinafter described. Since the signal intensity of anenergy component of the gain adjustment circuit 481 includes not only asignal component (spread code component) to be detected but also noiseand so forth, the gain value setting circuit 482 sets a reception gainvalue based on the signal intensity of the energy component of theentire signal to be detected by the reception conductor selectioncircuit 31.

The gain value setting circuit 482 is provided in order to control thegain adjustment circuit 481 based on an output signal converted into adigital signal by the A/D conversion circuit 33. The gain value settingcircuit 482 includes a gain value detection circuit 483 and an automaticgain control circuit 484.

The absolute value detection circuit 483 detects the signal intensity ofthe energy component of an output signal output from the A/D conversioncircuit 33. Since the signal output from the A/D conversion circuit 33includes not only the signal component (spread code component) to bedetected but also an unnecessary signal component such as noise, thegain adjustment circuit 481 detects the signal intensity of the energycomponent of the entire detection signal which includes an unnecessarysignal component such as noise.

The automatic gain control circuit 484 controls the gain of the gainadjustment circuit 481 based on the signal intensity detected by theabsolute value detection circuit 483. The automatic gain control circuit484 is connected to the absolute value detection circuit 483 and thegain adjustment circuit 481, and outputs a control signal to the gainadjustment circuit 481.

Next, a configuration of the absolute value detection circuit 483 isdescribed with reference to FIG. 64. The absolute value detectioncircuit 483 includes an accumulator 483 a, and another integrator 483 bconnected to an output terminal of the accumulator 483 a.

The accumulator 483 a performs squaring calculation of an output signalof the A/D conversion circuit 33 and outputs an output signal obtainedby the calculation to the integrator 483 b. It is to be noted that anoutput signal of the A/D conversion circuit 33 shown in FIG. 63 isbranched and input to two input terminals of the accumulator 483 a sothat the branched signals are multiplied by the accumulator 483 a. Theintegrator 483 b temporally integrates an output signal of theaccumulator 483 a and outputs a resulting integration signal as acontrol signal to the automatic gain control circuit 484 and then to thegain adjustment circuit 481 shown in FIG. 63.

As described above, in setting the reception gain value in the presentmodification 26, the signal intensity of an energy component of asignal, which includes not only the signal component (spread codecomponent) to be detected but also noise and so forth, is detected andthe reception gain value is set based on the signal intensity. Thus,even if noise and so forth are superposed on the output signal input tothe gain adjustment circuit 481, the reception gain value can be setoptimally.

It is to be noted that, for the absolute value detection, any othersuitable method can be used as long as the method can detect the levelof a signal including both a signal component to be detected and noise.For example, in addition to the technique described above, a techniquesuch as integrating the absolute value of the level of the output signalcan be used. Further, as the absolute value detection process, either adigital signal process after A/D conversion or an analog signal processbefore A/D conversion may be used.

[Modification 27]

The pointer detection apparatus of the present invention makes itpossible to detect a plurality of pointers such as fingers at the sametime. Therefore, for example, the pointer detection apparatus of thepresent invention may be used by a plurality of users at the same timeor may be operated by both hands of one user. As a result, the scale ofthe sensor section may become large in order to allow use of the sensorsection with a plurality of pointers.

The embodiments and the modifications described hereinabove areconfigured such that the spread codes C_(k) are supplied to one ends ofthe transmission conductors 12. However, if the scale of the sensorsection increases, then the length of the transmission conductors 12which serve as transmission lines for the spread codes C_(k) as well asthe length of the reception conductors 14 which serve as transmissionlines for output signals increases correspondingly to the increase inthe scale of the sensor section. Then, floating capacitance of thetransmission lines for the spread codes C_(k) may cause a drop of thelevel of the output signals or a delay in the phase of the detectionsignals. This problem is described particularly with reference to FIGS.65A and 65B.

FIG. 65A illustrates a case where a spread code C_(k) is supplied to anarbitrary transmission conductor Y_(k), and FIG. 65B illustrates avariation of the signal level and the phase of a detection signalobtained with each reception conductor 14 when the spread code C_(k) issupplied to the transmission conductor Y_(k). It is to be noted that, inFIG. 65B, the axis of abscissa indicates the positions of receptionconductors 14 and the axis of ordinate indicates the level of thedetection signal and the phase. Further, FIG. 65B indicates thevariation of detection signals from five reception conductors 14, thatis, the reception conductors X_(m), X_(m+2), X_(m+4), X_(m+6) andX_(m+8), for simplified illustration and description.

As seen in FIG. 65A, if the spread code C_(k) of a supply signal issupplied to one end of the transmission conductor Y_(k), that is, in theexample of FIG. 65A, to the right end of the transmission conductor 12,then the signal level of the output signal of the reception conductors14 drops by an increasing amount as the distance from the supply side ofthe spread code C_(k) increases, that is, from the reception conductorX_(m+8) positioned closest to the supply side toward the receptionconductor X_(m) positioned farther away from the supply side, due to theinfluence of the floating capacitance of the transmission conductorY_(k) serving as a transmission line. Similarly, the phase delay of theoutput signal increases as the distance from the supply side of thespread code C_(k) increases.

As a result, both the signal level and the phase of the output signaldecrease, starting from the reception conductor X_(m+8) to the receptionconductor X_(m), as seen in FIG. 65B. Thus, the signal level differenceand the phase difference of the output signals which appear between thereception conductor X_(m+8) and the reception conductor X_(m) make itdifficult to calculate an accurate correlation value for positiondetection purposes, resulting in a drop in the detection sensitivity.Particularly, in the sensor section where an ITO film is used for thetransmission conductors 12 and the reception conductors 14, theresistance value of the conductors is high, and the problem such as adrop in the signal level or a delay of the phase of the output signalbecomes exacerbated.

Therefore, the present modification 27 is directed to a supplying methodof a spread code which can eliminate the problem described above and isdescribed with reference to FIGS. 66A and 66B. FIGS. 66A and 66Billustrate a supply pattern of a spread code C_(k) in the presentmodification 27 and a variation characteristic of the level and thephase of the output signal.

The present modification 27 is different from the embodiments and themodifications described hereinabove in that the same spread code C_(k)is supplied at the same time to the opposite ends of one transmissionconductor Y_(k), as seen in FIG. 66A. In order to implement this supplypattern, for example, in the configuration of the first embodiment, eachoutput terminal of the spread code supplying circuit 21 shown in FIG. 1is connected to the opposite ends of the transmission conductor Y_(k).

Where the same spread code C_(k) is supplied at the same time to theopposite ends of the transmission conductor Y_(k) in this manner, thedistance from the supply side of the spread code C_(k), that is, fromthe opposite ends of the transmission conductor 12, to the receptionconductor 14 positioned farthest, which is the centrally-locatedreception conductor X_(m+4) in FIG. 66A, becomes one half of that in analternative case where the spread code C_(k) is supplied only to one endof the transmission conductor Y_(k). As a result, although the level ofthe output signal is lowest at the reception conductor X_(m+4)positioned farthest from the supply side of the spread code C_(k), thatis, from the opposite ends of the transmission conductor 12, thedecreasing amount of the signal level and the phase delay of the outputsignal can be reduced in comparison with an alternative case wherein thespread code C_(k) is supplied only to one end of the reception conductor14. Consequently, the level difference and the phase difference amongthe reception conductors 14 are minimized, and the detection sensitivitycan be maintained.

[Modification 28]

The modification 28 is directed to a method suitable to detect pressingforce (hereinafter referred to as “pointing pressure”) when a pointersuch as a finger touches the detection surface of the sensor section ofthe pointer detection apparatus of the present invention.

According to a conventional technique, the pointing pressure iscalculated based on the contact area between the pointer and thedetection surface of the sensor section. However, the conventionaltechnique is disadvantageous in that, for example, when a user having athin finger strongly touches (with force) the detection surface of thesensor section, since the contact area remains relatively small, thetouch is detected as a light touch.

Therefore, in the present modification 28, in order to eliminate such aproblem as described above, the pointing pressure is detected using aspatial distribution or mapping data of the level of a detection signal(correlation value) at each cross point obtained upon position detectionof a pointer. In the following, this technique is described particularlywith reference to FIGS. 1, 67 and 68. It is to be noted that thedetection of the pointing pressure is carried out by the positiondetection circuit 35 of the reception section 300 described hereinabovewith reference to FIG. 1.

FIG. 67 illustrates a spatial variation of the level of the signal(correlation value) stored in the correlation value storage circuit 34 dshown in FIG. 8 when a pointer touches the detection surface of thesensor section 100 shown in FIG. 2. In FIG. 67, the axis of abscissarepresents the positions of the reception conductors 14 and the axisextending into the surface of the figure represents the positions of thetransmission conductors 12, while the axis of ordinate represents thelevel of the detection signal (correlation value). It is to be notedthat the level on the axis of ordinate is represented in a normalizedvalue. Further, in the example illustrated in FIG. 67, a spatialdistribution of the level of the detection signal is shown, where apointer touches a cross point between the transmission conductor Y_(n)and the reception conductor X_(m), and a spatial distribution of thelevel only in an area defined by the transmission conductors Y_(n−4) toY_(n+4) and the reception conductors X_(m−4) to X_(m+4) is shown forsimplified illustration and description.

First, the position detection circuit 35 reads out the mapping data ofthe signal stored in the correlation value storage circuit 34 d andapplies an interpolation process or the like to the signal levels of theoutput signals at the cross points, thereby interpolating the signallevels between the cross points. Then, the position detection circuit 35calculates a mountain-shaped level curved surface 490 which exhibits anapex or peak at the cross point [X_(m), Y_(n)] at which the pointertouches. While, in the example illustrated in FIG. 67, the level curvedsurface 490 is produced by applying an interpolation process or the liketo the signal level of the output signal at each cross point,alternatively, the correlation values determined for the respectivecross points may be first interpolated and the resulting interpolateddata may be stored as mapping data in the correlation value storagecircuit 34 d, which may thereafter be used to produce the level curvedsurface 490.

Thereafter, a signal process of cutting the level curved surface 490along a predetermined level plane 490 a represented as a regionindicated by slanting lines in FIG. 67 is carried out. Furthermore,another signal process of determining the volume of a region surroundedby the level curved surface 490 is carried out. It is to be noted herethat the area of the level plane 490 a is the contact area of thepointer.

Here, a method of simply determining the volume of the region surroundedby the level curved surface 490 is described with reference to FIG. 68.First, the level curved surface 490 is divided into planes extendingalong the extension direction of the transmission conductors 12, as seenin FIG. 67. Consequently, divisional planes 491 to 499 are produced, forexample, along the extension direction of the transmission conductorsY_(n−4) to Y_(n+4) as seen in FIG. 68.

Then, the areas Sa₁ to Sa₉ of the divisional planes 491 to 499 aredetermined. The calculated areas Sa₁ to Sa₉ are added, and a resultingsum value is used as an approximate value of the volume of the regionsurrounded by the level curved surface 490. The volume of the regionsurrounded by the level curved surface 490 has a value corresponding tothe pointing pressure, and if the pointing pressure increases, then thevolume correspondingly increases. Therefore, the pointing pressure canbe determined based on the volume of the region surrounded by the levelcurved surface 490. In the present modification 28, the pointingpressure of the pointer is determined by carrying out the signalprocessing as just described.

It is to be noted that the volume of the region surrounded by the levelcurved surface 490, determined in the manner described above, mayfurther be divided by the contact area. In this instance, a valuecorresponding to the pointing pressure per unit area of the contact areais calculated.

As described above, in the present modification 28, when a pointertouches the detection surface of the sensor section 100, the positiondetection circuit calculates a three-dimensional level curved surface ofthe detection signal (correlation value), and the volume of a regionsurrounded by the level curved surface is calculated to determine thepointing pressure. Therefore, the problem associated with theconventional pointing pressure detection method described hereinabovecan be eliminated, and a pointing pressure that corresponds to theuser's actual touch (a light touch, a strong touch, etc.) can bedetected.

In the detection method of the pointing pressure described above, thelevel curved surface 490 is divided into a plurality of planes and thesum of the areas of the plural divisional planes, that is, anintegration value of the areas, is determined and used as the volume ofthe level curved surface 490. The present invention, however, is notlimited to this configuration. In order to calculate the volume of thelevel curved surface 490 with a higher degree of accuracy, the levelvalues may be weighted-added as in a numerical analysis method. Further,the calculation method of the volume is not limited to the summing ofdivisional planes, and multi-dimensional curved surface approximationmethods such as trapezoid approximation or square approximation methodsmay be used to calculate the volume.

Next, a procedure of determining the region surrounded by the levelcurved surface 490 using trapezoid approximation is described withreference to FIG. 69, wherein the areas of the divisional planes areweighted-added.

FIG. 69 illustrates a relationship between the positions of transmissionconductors 12 and the areas Sa₁ to Sa₉ of the divisional planes 491 to499 of the level curved surface 490 determined by the techniquedescribed hereinabove with reference to FIG. 69. In FIG. 69, the axis ofabscissa indicates the positions of the transmission conductors 12, andthe axis of ordinate indicates the areas of the divisional planes. Acurve 495 in FIG. 69 is formed by joining data points of the areas Sa₁to Sa₉.

The volume of the region surrounded by the level curved surface 495corresponds to the area of a region surrounded by the axis of abscissaand the curve 495 in FIG. 69. Further, if adjacent data points of theareas Sa₁ to Sa₉ in FIG. 69 are interconnected by straight lines, thenfour trapezoidal regions are formed in the area between the transmissionconductors Y_(n−2) to Y_(n+2). In the trapezoid approximation, the areaof the portion surrounded by the axis of abscissa and a curve 495 inFIG. 69 is approximated as a sum value of the areas of the fourtrapezoidal regions formed between the transmission conductors Y_(n−2)to Y_(n+2) in FIG. 69. More particularly, the volume is determined inthe following manner.

First, a weight value is applied to each of the data points S_(a3) toS_(a7) which define the region indicated by slanting lines in FIG. 69 inaccordance with the trapezoidal approximation. For example, the weight 1is applied to the data point S_(a3); the weight 2 to the data pointS_(a4); the weight 2 to the data point S_(a5); the weight 2 to the datapoint S_(a6); and the weight 1 to the data point S_(a7). Then, thevolume V₁ of the level curved surface 490 is determined by dividing the“sum value of the areas of the weighted divisional planes” by the“average value of the weight values included in the trapezoidal shapes.”In particular, the volume V₁ of the level curved surface 490 is givenby:Volume V ₁=(1×S _(a3)+2×S _(a4)+2×S _(a5)+2×S _(a6)+1×S _(a7))/2Here, the “average value of the weight values,” which is the denominatorof the expression above, is determined by dividing the “sum total of theweight values at the data points” by the “number of the trapezoids.” Inthe example above, (1+2+2+2+1)/4=2.

If the method of the trapezoid approximation described above is used,then since the error (offset) between the hypotenuses which form thefour trapezoids in FIG. 69 and the curve 495 is small, the error betweena result of calculation obtained using the trapezoid approximation, thatis, the area of the slanting line portion, and the actual volume of thelevel curved surface 490 is also small. Therefore, by using thetechnique described above, the volume of the level curved surface 490can be determined relatively accurately. Further, by determining thevolume of the level curved surface 490 using such approximationcalculation, the calculation load to be applied to the positiondetection circuit 35 can be reduced.

Further, in the method described above of weighted-adding the divisionalplanes, the square approximation may be used in place of the trapezoidapproximation. In this instance, to the data points S_(a3) to S_(a7)which form the region indicated by slanting lies in FIG. 69, weightedvalues are applied in accordance with square approximation. For example,the weight 1 is applied to the data point S_(a3); the weight 4 to thedata point S_(a4); the weight 2 to the data point S_(a5); the weight 4to the data point S_(a6); and the weight 1 to the data point S_(a7). Inthis instance, the volume V₂ of the level curved surface 490 is givenby:Volume V ₂=(1×S _(a3)+4×S _(a4)+2×S _(a5)+4×S _(a6)+1×S _(a7))/3Here, the “average value of the weight values,” which is the denominatorof the expression above, is determined by dividing the “sum total of theweight values at the data points” by the “number of the trapezoids” andis (1+4+2+4+1)/4=3.[Modification 29]

In the embodiments and the modifications described above, a number ofspread codes C_(k) smaller than the number of transmission conductors 12are used and selectively supplied to the transmission conductors 12.However, for example, a number of different spread codes C_(k) equal tothe number of the transmission conductors 12 may be used such that thespread codes C_(k) and the transmission conductors 12 correspond in aone-to-one corresponding relationship to each other without thenecessity for switching the transmission conductors 12 to which thespread codes C_(k) are to be supplied.

FIG. 70 illustrates an example wherein a number of spread codes equal tothe number of transmission conductors are used and supplied to therespective different transmission conductors. Accordingly, in thepresent modification 29, the transmission conductor selection circuit 22described hereinabove with reference to FIG. 1 is not required,similarly as in the second embodiment described hereinabove withreference to FIG. 20.

In the present modification 29, in order to supply a number of spreadcodes C_(k) equal to the number of the transmission conductors 12, thatis, 64 different spread codes C_(k), the number of chips forming eachspread code C_(k) must be set to greater than 16 chips, which are usedin the first embodiment described above, for example, to 64 chips orgreater.

FIG. 71 shows a configuration of the correlation value calculationcircuit 334 in the present modification 29. The correlation valuecalculation circuit 334 in the present modification 29 is different fromthe correlation value calculation circuit 34 in the first embodiment inthat a signal delay circuit 334 a provided in the correlation valuecalculation circuit 334 is composed of 64 D-flip-flop circuits 334 a ₁to 334 a ₆₄ and that the number of correlators 334 b for calculatingcorrelation values and the number of correlation value calculation codeproduction circuits 334 c for supplying correlation value calculationcodes to the correlators 334 b are equal to the number of the spreadcodes C_(k), that is, 64. It is to be noted that the configuration ofthe other part of the correlation value calculation circuit 334 in thepresent modification 29 is the same as that of the correlation valuecalculation circuit 34 in the first embodiment described hereinabovewith reference to FIG. 8, and overlapping description of the same isomitted herein to avoid redundancy.

In the correlation value calculation circuit 334, the 64 correlators 334b ₁, 334 b ₂, 334 b ₃, . . . , 334 b ₆₄ respectively multiply the 64spread codes C₁ to C₆₄ illustrated in FIG. 71 by correlation valuecalculation codes C₁′ to C₆₄′, which respectively correspond to thespread codes C₁ to C₆₄, to calculate correlation values of the spreadcodes. In particular, the correlator 334 b ₁ calculates a correlationvalue by multiplication of the spread code C₁ by the correlation valuecalculation code C_(1A)′, and the correlator 334 b ₂ calculates acorrelation value by multiplication of the spread code C₂ and thecorrelation value calculation code C_(2A)′. Similar multiplication iscarried out until a correlation value is calculated with regard to allof the 64 spread codes C₁ to C₆₄. The calculated correlation values arestored in the correlation value storage circuit 334 d.

Where the correlation values are calculated by the correlation valuecalculation circuit 334 shown in FIG. 71, since there is no necessity toswitch between the transmission conductors 12 to which the spread codesC_(k) are to be supplied, the configuration of the transmission section200 can be further simplified.

While, in the present modification 29, a number of spread codes C_(k)equal to the number of the transmission conductors 12 are used, thepresent invention is not limited to this configuration. For example, thesame spread code C_(k) may be supplied, for example, to two transmissionconductors 12 positioned adjacent to each other as in the case of themodification 13 described hereinabove with reference to FIG. 41. In thisinstance, a number of spread codes C_(k) need not equal the number ofthe transmission conductors 12, and a number of spread codes C_(k) needequal only one half of the number of transmission conductors 12. Inother words, 32 spread codes C_(k) can be used while similar effects canbe achieved.

[Modification 30]

When a pointer touches a cross point between a transmission conductorand a reception conductor, the variation of the capacitance value whichappears at the cross point is very small. For example, while thecapacitance value at a cross point when the pointer 19 does not touchthe sensor section 100 is 0.5 pF, the variation amount of thecapacitance value at the cross point when the pointer 19 touches thesensor section 100 is approximately 0.05 pF.

For example, an output signal obtained from an arbitrary one of thereception conductors 14 where a code string of a 2n-chip length issupplied exhibits the highest signal level when the mth chip (m is anatural number equal to or higher than 1 but equal to or lower than n)of each of all code strings supplied to the transmission conductors 12is “1.” This is because the signal level of the output signal increasesin proportion to the sum of values obtained by multiplying thecapacitance values at the cross points with the chips supplied to thecross points. Accordingly, for example, if Hadamard codes of a 16-chiplength shown in FIG. 17A are supplied, then the output signal obtainedfrom the reception conductor 14 exhibits the highest signal level whenthe 1st chips (all “1”) of the Hadamard codes of the 16-chip length aresupplied to the reception conductor 14.

On the other hand, the signal level of the output signal obtained whenthe pointer 19 touches a cross point is equal to the output signal inthe form of a current signal obtained when the pointer 19 does not touchthe cross point minus a current signal shunted through the pointer 19 atthe cross point. Since the variation amount of the capacitance value atthe cross point when the pointer 19 touches the cross point is verysmall, the variation amount of the current signal is very small. Inorder to detect the very small variation of the current signal, it isnecessary to use an amplifier having a high amplification factor in theamplification circuit.

However, if an amplifier having an amplification factor suitable for theoutput signal obtained when the pointer 19 is touching is used, then anew problem arises whereby the output signal obtained when the 1st chipof the Hadamard code of the 16-chip length is supplied to the receptionconductor 14 gets clipped. Conversely, if an amplifier having anamplification factor suitable for the output signal obtained when the1st chip of the Hadamard code of the 16-chip length is supplied to thereception conductor 14 is used, then another problem arises whereby avery small variation of the output signal cannot be detected.

When code strings of the 2n-chip length which are different from eachother are supplied to different transmission conductors 12, since theproblem described above appears when all of the mth chips of the codestrings are “1,” if the mth chips (all “1”) are prevented from beingsupplied to the transmission conductors 12, then the maximum value ofthe signal level of the output signal can be suppressed low. Inparticular, if the Hadamard codes of the 15-chip length illustrated inFIG. 17B are supplied, then the maximum value of the output signal canbe suppressed lower by a value equal to the number of the Hadamard codessupplied to the transmission conductors 12. Thus, in the case of theHadamard codes illustrated in FIG. 17B (16 Hadamard codes), the maximumvalue of the output signal can be suppressed by “16.” In this instance,the level of the correlation value obtained when the Hadamard codes ofthe 15-chip length are supplied to the transmission conductors 12 isalso suppressed to a fixed low level when the pointer 19 is not placedat any cross point of the reception conductor 14. The fixed level of thecorrelation value described above is hereinafter referred to as a“reference level.”

However, where the Hadamard codes of the 15-chip length are supplied tothe transmission conductors 12, a new problem arises that, if thepointer 19 touches a cross point, then the reference level varies. Thisis because, since the Hadamard codes of the 15-chip length are shorterin code length by one chip than the Hadamard codes of the 16-chiplength, if the pointer 19 touches a cross point, then the referencelevel increases by an amount corresponding to the amount of currentshunted at the cross point to the ground. Accordingly, if the pointer 19touches a plurality of cross points at the same time, then the referencelevel varies by an amount corresponding to the number of the crosspoints touched by the pointer 19.

The decision of whether or not the pointer 19 touches a cross point iscarried out, for example, by comparing the signal level of the outputsignal with a predetermined threshold value (see FIGS. 16A and 16B).Since the pointer detection apparatus according to the present inventioncan detect a plurality of pointers at the same time, for example, thepalm of the hand may possibly be placed on the sensor section 100, or aplurality of pointers such as, for example, a plurality of fingers, maypossibly touch a plurality of cross points on the same receptionconductor array 13 at the same time. In those cases, the reference levelof the output signal of the reception conductor 14 varies by a greatamount. As a result, the level of the correlation value at the crosspoint which the pointer 19 touches may vary by a great amount such thatthe signal level of the output signal will not exceed the thresholdvalue, resulting in wrong decision.

In the following, a modification 30 which solves the problem describedabove is described with reference to FIGS. 72 and 73. The pointerdetection apparatus 3 according to the present modification 30 issimilar to the pointer detection apparatus 1 according to the firstembodiment described hereinabove with reference to FIG. 1 except thatthe spread code supplying circuit 21 and an amplification circuit 332are connected to each other in order to supply one of the spread codesC_(k), which are supplied from the spread code supplying circuit 21 tothe sensor section 100, directly to the amplification circuit 332. It isto be noted that the reception conductor selection circuit 31 is omittedin FIG. 73 in order to avoid complicated illustration. Further, for easeof understanding, only a region of the sensor section 100 where thetransmission conductors Y₁ to Y₆ cross the reception conductors X₁₂₃ toX₁₂₈ is shown in FIG. 73, and the following description is given inregard to a case in which the spread codes C_(k) are respectivelysupplied to the transmission conductors Y₁ to Y₆ and output signals fromthe reception conductors X₁₂₃ to X₁₂₈ are detected. It is to be notedthat like components to those of the pointer detection apparatus 1 ofthe first embodiment are denoted by like reference characters andoverlapping description of the like components is omitted herein toavoid redundancy.

Referring first to FIG. 72, the spread code supplying circuit 21 isconnected to an amplification circuit 332 in addition to a transmissionconductor selection circuit 22, a clock generation circuit 23, acorrelation value calculation circuit 34, and a control circuit 40. Fromamong a plurality of spread code production circuits 24 which form thespread code supplying circuit 21, for example, an arbitrary spread codeproduction circuit 24 is connected to the amplification circuit 332. Aspread code, for example, the spread code C₁, output from the spreadcode production circuit 24 connected directly to the amplificationcircuit 332 is supplied directly to the amplification circuit 332 of areception section 340 without passing through any transmission conductor12 so that the spread code C₁ is used as a calibration signal or areference signal having a reference level for correlationcharacteristic.

The reception section 340 in the modification 30 is described withreference to FIG. 73. The amplification circuit 332 includes the numberof I/V conversion circuits 332 a equal to the number of receptionconductors 14, and the number of capacitors 332 b equal to the number ofI/V conversion circuits 332 a. The capacitors 332 b are provided betweenthe spread code production circuit 24 (not shown) for generating thespread code C₁ and the I/V conversion circuits 332 a. Accordingly, thespread code C₁ is supplied to the I/V conversion circuits 332 a throughthe capacitors 332 b. It is to be noted that spread code productioncircuits 24 which generate the other spread codes C₂ to C₇ are connectedto the transmission conductors Y₁ to Y₆, respectively.

Since the spread code C₁ is supplied to the capacitors 332 b, outputsignals output from the reception conductors 14 are combined withcurrent signals (calibration signals) generated when the spread code C₁is supplied to the capacitors 332 b and are input to the I/V conversioncircuits 332 a. The output signals combined with the calibration signalare converted into voltage signals, amplified, and output by the I/Vconversion circuits 332 a.

An A/D conversion circuit 333 includes the number of A/D converters 333a equal to the number of I/V conversion circuits 332 a which form theamplification circuit 332. Each of the A/D converters 333 a is connectedto a corresponding one of the I/V conversion circuits 332 a. A voltagesignal output from each of the I/V conversion circuits 332 a is input tothe A/D conversion circuit 333, by which it is converted into a digitalsignal. The digital signal is output to a position detection circuit 35shown in FIG. 72.

The correlation value calculation circuit 34 carries out correlationcalculation with correlation value calculation codes corresponding tothe spread codes. Here, since the spread code C₁ is directly input tothe amplification circuit 332 which forms the reception section 340without passing through any of the transmission conductors 12 and thereception conductors 14, signal components of the spread code C₁ do notinclude a variation factor introduced by the transmission conductors 12and the reception conductors 14. As a result, a result of thecorrelation calculation based on a correlation value calculation codeC₁′ corresponding to the spread code C₁, that is, a correlation value,is a value which is fixed and always stable.

In the present modification 30, this fixed correlation value is used asa reference level. In particular, the correlation value calculationcircuit 34 carries out correlation calculation with the correlationvalue calculation code C₁′ of the spread code C₁ for the digital signalsinput from the A/D conversion circuit 333. Then, a correlation valueobtained by the correlation calculation is stored as a reference levelof correlation characteristics, for example, in the correlation valuestorage circuit 34 d shown in FIG. 8. Thereafter, the correlation valuecalculation circuit 34 carries out correlation calculation regarding thecorrelation value calculation codes C₂′ to C₇′ corresponding to thespread codes C₂ to C₇, respectively, similarly as in the firstembodiment described hereinabove, and stores correlation values whichare the results of the calculation in the correlation value storagecircuit 34 d.

Then, the position detection circuit 35 (see FIG. 1) determines whetheror not a pointer 19 is touching the sensor section 100 based on thecorrelation values, which are calculated in regard to the spread codesC₂ to C₇ and stored in the correlation value storage circuit 34 d, thecorrelation value corresponding to the reference level for correlationcharacteristics, and a predetermined threshold value. In particular, theposition detection circuit 35 subtracts the value of the reference levelfor correlation characteristics from the correlation values calculatedwith regard to the spread codes C₂ to C₇. Then, the position detectioncircuit 35 compares the resulting difference values with thepredetermined threshold value to determine whether or not one or morepointers 19 exist on the sensor section 100.

By supplying a predetermined one of a plurality of spread codes to thereception section directly without going through any of the transmissionconductors 12 and the reception conductors 14 and using the spread codeas a calibration signal or a reference signal for the reference levelfor correlation characteristics in this manner, even if variation occurswith the reference level, a touched position of the pointer 19 can bedetected accurately.

[Modification 31]

In the modification 30 described above, output signals from thereception conductors and the calibration signal are combined while theyremain in the form of an analog signal before they are input to the A/Dconversion circuit. Where the calibration signal and the output signalsare combined in the form of an analog signal, since this can beimplemented with only the capacitors 332 b, the circuit configurationcan be simplified.

However, it is necessary for the capacitors 332 b to have a capacitancevalue set so as to be substantially equal to that of the capacitorsformed between the transmission conductors 12 and the receptionconductors 14. Since the capacitance of a capacitor formed at a crosspoint between a transmission conductor 12 and a reception conductor 14is approximately 0.5 pF and very low, it is difficult to mount suchcapacitors on an actual circuit board. Further, in the modification 30,since the calibration signal and the reception signals are combinedwhile they remain in the form of an analog signal, an error may beintroduced.

Therefore, in the present modification 31, the calibration signal iscombined with output signals of the A/D conversion circuit, that is,with reception signals after being converted into digital signals.

An example of a configuration for combining a calibration signal andreception signals having been converted into digital signals isdescribed with reference to FIG. 74. The present modification 31includes, between the A/D conversion circuit 433 and the correlationvalue calculation circuit 34 (see FIG. 72), an adder array 434 thatcombines digital signals output from the A/D conversion circuit 433 witha calibration signal converted into a digital signal. The presentmodification 31 also includes a capacitor 435, an I/V conversion circuit436, and an A/D converter 437. The capacitor 435 supplies a spread codeto be used as a calibration signal directly to the reception section.The I/V conversion circuit 436 converts a current signal into a voltagesignal. The A/D converter 437 converts the calibration signal into adigital signal. The other components are similar to those of themodification 30 described hereinabove with reference to FIG. 72, andlike elements are denoted by like reference characters, and overlappingdescription of the same is omitted herein to avoid redundancy.

When the spread code C₁ is supplied to the capacitor 435, a currentsignal is supplied to the I/V conversion circuit 436. The I/V conversioncircuit 436 converts the current signal input thereto into a voltagesignal and amplifies and outputs the voltage signal. The voltage signaloutput from the I/V conversion circuit 436 is converted into a digitalsignal by the A/D converter 437 and then input to the adder array 434.

The adder array 434 is formed of a number of adders 434 a equal to thenumber of A/D converters 433 a which form the A/D conversion circuit433. Each of the adders 434 a is interposed between an A/D converter 433a connected to the reception conductors 14 and an input terminal of thecorrelation value calculation circuit 34 such that the adders 434 areceive a digital signal output from each of the A/D converters 433 aand the calibration signal also converted into a digital signal by theA/D converter 437. Then, the adders 434 a combine (add) the outputsignals and the calibration signal, respectively, and output thecombined digital signals.

The digital output signals combined with the calibration signal by theadders 434 a are then input to the correlation value calculation circuit34. The correlation value calculation circuit 34 carries out correlationcalculation.

In the configuration example described above with reference to FIG. 74,adjustment of the reference level can be carried out similarly as in theexample shown in FIG. 73. In the present modification 31, since thecalibration signal and the reception signals are combined as digitalsignals, by using a capacitor of, for example, 8 pF, as the capacitor435 provided for supplying the calibration signal (8 pF being 16 timesthe capacitance of 0.5 pF at each cross point between a transmissionconductor 12 and a reception conductor 14) and by dropping 4-bits worthof data in the A/D converter 437, signal combination can be achievedwith a higher degree of accuracy than where such combination is carriedout in analog signals.

a capacitor of 0.5 pF is formed at each of the cross points between thetransmission conductor array 11 and the reception conductor array 13.

It is to be noted that, while, in the present embodiment 31, one spreadcode is used as a calibration signal for adjusting the reference level,the present invention is not limited to this configuration. For example,two or more spread codes may be supplied as calibration signals.

While preferred embodiments of the present invention have been describedusing specific terms, such description is for illustrative purposesonly, and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the following claims.

What is claimed is:
 1. A pointer detection apparatus for detecting apointer positioned on a conductor pattern, the conductor patternincluding a plurality of first conductors disposed in a first directionand a plurality of second conductors disposed in a second directionwhich crosses the first direction, the pointer detection apparatuscomprising: a code supplying circuit having a plurality of code stringsof different codes from each other, the code supplying circuit beingconfigured to supply predetermined ones of the code strings to the firstconductors disposed in the first direction; a correlation calculationcode supplying circuit configured to supply correlation calculationcodes that respectively correspond to the code strings; a correlationcalculation circuit configured to carry out correlation calculationbetween signals produced in the second conductors disposed in the seconddirection and the correlation calculation codes; a detection circuitconfigured to detect the pointer positioned on said conductor patternbased on a level curve that results from the correlation calculation,the detection circuit being further configured to: (a) apply logarithmicconversion to the level curve; (b) determine a ratio between a gradientof an edge and a peak value of the level curve to which the logarithmicconversion is applied; (c) determine the pointer to be in a firsthovering state at or beyond a first distance away from the conductorpattern if the ratio is at or below a first threshold value; (d)determine the pointer to be in a second hovering state at or within thefirst distance away from the conductor pattern if the ratio is at orabove the first threshold value and at or below a second threshold valuegreater than the first threshold value; and (e) determine the pointer tobe in contact with the conductor pattern if the ratio is at or above thesecond threshold value; and a conductor selection circuit configured toselect, (i) in case the detection circuit determines the pointer to bein contact with the conductor pattern, one of the first conductors towhich one of the code strings is supplied, and (ii) in case thedetection circuit determines the pointer to be in the first or secondhovering state, a plurality of the first conductors, which are connectedwith each other and to which one of the code strings is simultaneouslysupplied, and/or a plurality of the second conductors, which areconnected with each other and from which the signals are received by thecorrelation calculation circuit for correlation calculation, wherein thewidth for pointer detection formed by a plural number of the firstconductors to which said one of the code strings is simultaneouslysupplied is less than the width for pointer detection formed by a pluralnumber of the second conductors from which the signals are received forthe correlation calculation in case the first conductors are disposedfarther away from a detection surface of the apparatus than the secondconductors.
 2. The pointer detection apparatus according to claim 1,further comprising: a substrate having a surface on which said conductorpattern including the first conductors disposed in the first directionand the second conductors disposed in the second direction which crossesthe first direction is disposed; and an insulating member disposed in aregion in which the first conductors disposed in the first direction andthe second conductors disposed in the second direction which isorthogonal to the first direction cross each other, for electricallyisolating the first conductors disposed in the first direction from thesecond conductors disposed in the orthogonal direction; wherein thefirst conductors disposed in the first direction are formed in a patternhaving a plurality of land portions that are electrically connected toeach other; and wherein the second conductors disposed in the seconddirection are formed in a line-shaped pattern.
 3. The pointer detectionapparatus according to claim 1, further comprising: a substrate having asurface on which the first conductors disposed in the first directionare disposed and another surface on which the second conductors disposedin the second direction are disposed; wherein the first conductorsdisposed in the first direction are formed in a pattern having aplurality of land portions that are electrically connected to eachother; and wherein the second conductors disposed in the seconddirection are formed in a line-shaped pattern.
 4. The pointer detectionapparatus according to claim 1, wherein the first direction is aconcentric circumferential direction around a predetermined centralpoint, and the second direction is a radial direction extending from thecentral point.
 5. The pointer detection apparatus according to claim 1,wherein a contact state between the pointer and said conductor patternis determined based on a maximum value of the level curve and adistribution characteristic in the proximity of the maximum value. 6.The pointer detection apparatus according to claim 1, wherein thedetection circuit is further configured to detect pressure applied bythe pointer on said conductor pattern based on a spatial distribution ofthe level curve detected by said detection circuit.
 7. The pointerdetection apparatus according to claim 1, wherein a plural number of thefirst conductors to which said one of the code strings is simultaneouslysupplied is greater when the pointer is in the first hovering state thanwhen the pointer is in the second hovering state.
 8. A pointer detectionapparatus for detecting a pointer positioned on a conductor pattern, theconductor pattern including a plurality of first conductors disposed ina first direction and a plurality of second conductors disposed in asecond direction which crosses the first direction, the pointerdetection apparatus comprising: a code supplying circuit having aplurality of code strings of different codes from each other, the codesupplying circuit being configured to supply predetermined ones of theplurality of code strings to the first conductors disposed in the firstdirection; a correlation calculation circuit configured to carry outcorrelation calculation between signals produced in the secondconductors disposed in the second direction and correlation calculationcodes that respectively correspond to the code strings; a detectioncircuit configured to detect the pointer positioned on said conductorpattern based on a level curve that results from the correlationcalculation, the detection circuit being further configured to: (a)apply logarithmic conversion to the level curve; (b) determine a ratiobetween a gradient of an edge and a peak value of the level curve towhich the logarithmic conversion is applied; (c) determine the pointerto be in a first hovering state at or beyond a first distance away fromthe conductor pattern if the ratio is at or below a first thresholdvalue; (d) determine the pointer to be in a second hovering state at orwithin the first distance away from the conductor pattern if the ratiois at or above the first threshold value and at or below a secondthreshold value greater than the first threshold value; and (e)determine the pointer to be in contact with the conductor pattern if theratio is at or above the second threshold value; and a conductorselection circuit configured to select, (i) in case the detectioncircuit determines the pointer to be in contact with the conductorpattern, one of the first conductors to which one of the code strings issupplied, and (ii) in case the detection circuit determines the pointerto be in the first or second hovering state, a plurality of the firstconductors, which are connected with each other and to which one of thecode strings is simultaneously supplied, and/or a plurality of thesecond conductors, which are connected with each other and from whichthe signals are received by the correlation calculation circuit forcorrelation calculation, wherein the width for pointer detection formedby a plural number of the first conductors to which said one of the codestrings is simultaneously supplied is less than the width for pointerdetection formed by a plural number of the second conductors from whichthe signals are received for the correlation calculation in case thefirst conductors are disposed farther away from a detection surface ofthe apparatus than the second conductors.
 9. A pointer detection methodfor detecting a pointer positioned on a conductor pattern, the conductorpattern including a plurality of first conductors disposed in a firstdirection and a plurality of second conductors disposed in a seconddirection which crosses the first direction, the method comprising: acode supplying step for supplying predetermined ones of a plurality ofcode strings of different codes to the first conductors disposed in thefirst direction; a correlation calculation code supplying step forsupplying correlation calculation codes that respectively correspond tothe code strings; a correlation calculation processing step for carryingout correlation calculation between signals produced in the secondconductors disposed in the second direction and the correlationcalculation codes; a position detection step for detecting the pointerpositioned on the conductor pattern based on a level curve resultingfrom the correlation calculation, the position detection step including:(a) applying logarithmic conversion to the level curve; (b) determininga ratio between a gradient of an edge and a peak value of the levelcurve to which the logarithmic conversion is applied; (c) determiningthe pointer to be in a first hovering state at or beyond a firstdistance away from the conductor pattern if the ratio is at or below afirst threshold value; (d) determining the pointer to be in a secondhovering state at or within the first distance away from the conductorpattern if the ratio is at or above the first threshold value and at orbelow a second threshold value greater than the first threshold value;and (e) determining the pointer to be in contact with the conductorpattern if the ratio is at or above the second threshold value; and aconductor selection step for selecting, (i) in case the detectioncircuit determines the pointer to be in contact with the conductorpattern, one of the first conductors to which one of the code strings issupplied, and (ii) in case the pointer is determined to be in the firstor second hovering state, a plurality of the first conductors, which areconnected with each other and to which one of the code strings issimultaneously supplied, and/or a plurality of the second conductors,which are connected with each other and from which the signals arereceived for the correlation calculation, wherein the width for pointerdetection formed by a plural number of the first conductors to whichsaid one of the code strings is simultaneously supplied is less than thewidth for pointer detection formed by a plural number of the secondconductors from which the signals are received for the correlationcalculation in case the first conductors are disposed farther away froma detection surface of the apparatus than the second conductors.
 10. Thepointer detection method according to claim 9, wherein a plural numberof the first conductors to which said one of the code strings issimultaneously supplied is greater when the pointer is in the firsthovering state than when the pointer is in the second hovering state.